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Frequently asked questions: Knowledge Base

How do I prevent confounding variables from interfering with my research?: There are several methods you can use to decrease the impact of confounding variables on your research: restriction, matching, statistical control and randomization.
In restriction, you restrict your sample by only including certain subjects that have the same values of potential confounding variables.
In matching, you match each of the subjects in your treatment group with a counterpart in the comparison group. The matched subjects have the same values on any potential confounding variables, and only differ in the independent variable.
In statistical control, you include potential confounders as variables in your regression.
In randomization, you randomly assign the treatment (or independent variable) in your study to a sufficiently large number of subjects, which allows you to control for all potential confounding variables.
What is the difference between confounding variables, independent variables and dependent variables?: A confounding variable is closely related to both the independent and dependent variables in a study. An independent variable represents the suppose cause, while the dependent variable is the supposed effect. A confounding variable is a third variable that influences both the independent and dependent variables.
Failing to account for confounding variables can cause you to wrongly estimate the relationship between your independent and dependent variables.
Why do confounding variables matter for my research?: To ensure the internal validity of your research, you must consider the impact of confounding variables. If you fail to account for them, you might over- or underestimate the causal relationship between your independent and dependent variables, or even find a causal relationship where none exists.
Can I include more than one independent or dependent variable in a study?: Yes, but including more than one of either type requires multiple research questions.
For example, if you are interested in the effect of a diet on health, you can use multiple measures of health: blood sugar, blood pressure, weight, pulse, and many more. Each of these is its own dependent variable with its own research question.
You could also choose to look at the effect of exercise levels as well as diet, or even the additional effect of the two combined. Each of these is a separate independent variable.
To ensure the internal validity of an experiment, you should only change one independent variable at a time.
Can a variable be both independent and dependent?: No. The value of a dependent variable depends on an independent variable, so a variable cannot be both independent and dependent at the same time. It must be either the cause or the effect, not both!
What is an example of an independent and a dependent variable?: You want to find out how blood sugar levels are affected by drinking diet soda and regular soda, so you conduct an experiment.
The type of soda – diet or regular – is the independent variable.
The level of blood sugar that you measure is the dependent variable – it changes depending on the type of soda.
Why are independent and dependent variables important?: Determining cause and effect is one of the most important parts of scientific research. It’s essential to know which is the cause – the independent variable – and which is the effect – the dependent variable.
What is non-probability sampling?: In non-probability sampling, the sample is selected based on non-random criteria, and not every member of the population has a chance of being included.
Common non-probability sampling methods include convenience sampling, voluntary response sampling, purposive sampling, snowball sampling, and quota sampling.
What is probability sampling?: Probability sampling means that every member of the target population has a known chance of being included in the sample. Probability sampling methods include simple random sampling, systematic sampling, stratified sampling, and cluster sampling.
How do you avoid sampling bias?: Using careful research design and sampling procedures can help you avoid sampling bias. Oversampling can be used to correct undercoverage bias.
What are some types of sampling bias?: Some common types of sampling bias include self-selection, non-response, undercoverage, survivorship, pre-screening or advertising, and healthy user bias.
Why is sampling bias important?: Sampling bias is a threat to external validity – it limits the generalizability of your findings to a broader group of people.
What is sampling bias?: Sampling bias occurs when some members of a population are systematically more likely to be selected in a sample than others.
What is sampling error?: A sampling error is the difference between a population parameter and a sample statistic.
What’s the difference between a statistic and a parameter?: A statistic refers to measures about the sample, while a parameter refers to measures about the population.
When are populations used in research?: Populations are used when a research question requires data from every member of the population. This is usually only feasible when the population is small and easily accessible.
Why are samples used in research?: Samples are used to make inferences about populations. Samples are easier to collect data from because they are practical, cost-effective, convenient and manageable.
How do I cite a source with no author or page numbers in MLA?: If a source has no author, start the MLA Works Cited entry with the source title. Use a shortened version of the title in your in-text citation.
If a source has no page numbers, you can use an alternative locator (e.g. a chapter number or timestamp) to identify the relevant passage in your in-text citation. If the source has no numbered divisions, cite only the author’s name (or the title).
If you already named the author or title in your sentence, and there is no locator available, you don’t need a parenthetical citation:
Rajaram argues that representations of migration are shaped by “cultural, political, and ideological interests.”
The homepage of The Correspondent describes it as “a movement for radically different news.”
How do I cite a source with multiple authors in MLA?: In MLA Style, if a source has two authors, name both authors in your in-text citation and Works Cited entry. If there are three or more authors, name only the first author, followed by et al.
Number of authors In-text citation Works Cited entry
1 author (Moore 37) Moore, Jason W.
2 authors (Moore and Patel 37) Moore, Jason W., and Raj Patel.
3+ authors (Moore et al. 37) Moore, Jason W., et al.
When do I need to include an MLA in-text citation?: You must include an in-text citation every time you quote or paraphrase from a source (e.g. a book, movie, website, or article).
What are threats to external validity?: There are seven threats to external validity: selection bias, history, experimenter effect, Hawthorne effect, testing effect, aptitude-treatment and situation effect.
What are the two types of external validity?: The two types of external validity are population validity (whether you can generalize to other groups of people) and ecological validity (whether you can generalize to other situations and settings).
What is external validity?: The external validity of a study is the extent to which you can generalize your findings to different groups of people, situations, and measures.
What are the disadvantages of a cross-sectional study?: Cross-sectional studies cannot establish a cause-and-effect relationship or analyze behavior over a period of time. To investigate cause and effect, you need to do a longitudinal study or an experimental study.
Why do a cross-sectional study?: Cross-sectional studies are less expensive and time-consuming than many other types of study. They can provide useful insights into a population’s characteristics and identify correlations for further research.
Sometimes only cross-sectional data is available for analysis; other times your research question may only require a cross-sectional study to answer it.
How long is a longitudinal study?: Longitudinal studies can last anywhere from weeks to decades, although they tend to be at least a year long.
What is an example of a longitudinal study?: The 1970 British Cohort Study, which has collected data on the lives of 17,000 Brits since their births in 1970, is one well-known example of a longitudinal study.
What are the pros and cons of a longitudinal study?: Longitudinal studies are better to establish the correct sequence of events, identify changes over time, and provide insight into cause-and-effect relationships, but they also tend to be more expensive and time-consuming than other types of studies.
What is the difference between a longitudinal study and a cross-sectional study?: Longitudinal studies and cross-sectional studies are two different types of research design. In a cross-sectional study you collect data from a population at a specific point in time; in a longitudinal study you repeatedly collect data from the same sample over an extended period of time.
Longitudinal study Cross-sectional study
Repeated observations Observations at a single point in time
Observes the same group multiple times Observes different groups (a “cross-section”) in the population
Follows changes in participants over time Provides snapshot of society at a given point
What are threats to internal validity?: There are eight threats to internal validity: history, maturation, instrumentation, testing, selection bias, regression to the mean, social interaction and attrition.
What is internal validity?: Internal validity is the extent to which you can be confident that a cause-and-effect relationship established in a study cannot be explained by other factors.
How can I edit a paper that is over the word limit?: If you’ve gone over the word limit set for your assignment, shorten your sentences and cut repetition and redundancy during the editing process. If you use a lot of long quotes, consider shortening them to just the essentials.
If you need to remove a lot of words, you may have to cut certain passages. Remember that everything in the text should be there to support your argument; look for any information that’s not essential to your point and remove it.
What’s the difference between revising, proofreading, and editing?: Revising, proofreading, and editing are different stages of the writing process.
Revising is making structural and logical changes to your text—reformulating arguments and reordering information.
Editing refers to making more local changes to things like sentence structure and phrasing to make sure your meaning is conveyed clearly and concisely.
Proofreading involves looking at the text closely, line by line, to spot any typos and issues with consistency and correct them.
What is meant by model selection?: In statistics, model selection is a process researchers use to compare the relative value of different statistical models and determine which one is the best fit for the observed data.
The Akaike information criterion is one of the most common methods of model selection. AIC weights the ability of the model to predict the observed data against the number of parameters the model requires to reach that level of precision.
AIC model selection can help researchers find a model that explains the observed variation in their data while avoiding overfitting.
What is a model?: In statistics, a model is the collection of one or more independent variables and their predicted interactions that researchers use to try to explain variation in their dependent variable.
You can test a model using a statistical test. To compare how well different models fit your data, you can use Akaike’s information criterion for model selection.
How is AIC calculated?: The Akaike information criterion is calculated from the maximum log-likelihood of the model and the number of parameters (K) used to reach that likelihood. The AIC function is 2K – 2(log-likelihood).
Lower AIC values indicate a better-fit model, and a model with a delta-AIC (the difference between the two AIC values being compared) of more than -2 is considered significantly better than the model it is being compared to.
What is the Akaike information criterion?: The Akaike information criterion is a mathematical test used to evaluate how well a model fits the data it is meant to describe. It penalizes models which use more independent variables (parameters) as a way to avoid over-fitting.
AIC is most often used to compare the relative goodness-of-fit among different models under consideration and to then choose the model that best fits the data.
Should I include tables and figures in the reference list?: If you adapt or reproduce a table or figure from another source, you should include that source in your APA reference list. You should also acknowledge the original source in the note or caption for the table or figure.
Tables and figures you created yourself, based on your own data, are not included in the reference list.
Should I include lists of my tables and figures?: APA doesn’t require you to include a list of tables or a list of figures. However, it is advisable to do so if your text is long enough to feature a table of contents and it includes a lot of tables and/or figures.
A list of tables and list of figures appear (in that order) after your table of contents, and are presented in a similar way.
When should I use a table or figure to present data?: In an APA style paper, use a table or figure when it’s a clearer way to present important data than describing it in your main text. This is often the case when you need to communicate a large amount of information.
Before including a table or figure in your text, always reflect on whether it’s useful to your readers’ understanding:
Could this information be quickly summarized in the text instead?
Is it important to your arguments?
Does the table or figure require too much explanation to be efficient?
If the data you need to present only contains a few relevant numbers, try summarizing it in the text. If describing the data makes your text overly long and difficult to read, a table or figure may be the best option.
What is a factorial ANOVA?: A factorial ANOVA is any ANOVA that uses more than one categorical independent variable. A two-way ANOVA is a type of factorial ANOVA.
Some examples of factorial ANOVAs include:
Testing the combined effects of vaccination (vaccinated or not vaccinated) and health status (healthy or pre-existing condition) on the rate of flu infection in a population.
Testing the effects of marital status (married, single, divorced, widowed), job status (employed, self-employed, unemployed, retired), and family history (no family history, some family history) on the incidence of depression in a population.
Testing the effects of feed type (type A, B, or C) and barn crowding (not crowded, somewhat crowded, very crowded) on the final weight of chickens in a commercial farming operation.
How is statistical significance calculated in an ANOVA?: In ANOVA, the null hypothesis is that there is no difference among group means. If any group differs significantly from the overall group mean, then the ANOVA will report a statistically significant result.
Significant differences among group means are calculated using the F statistic, which is the ratio of the mean sum of squares (the variance explained by the independent variable) to the mean square error (the variance left over).
If the F statistic is higher than the critical value (the value of F that corresponds with your alpha value, usually 0.05), then the difference among groups is deemed statistically significant.
What is the difference between a one-way and a two-way ANOVA?: The only difference between one-way and two-way ANOVA is the number of independent variables. A one-way ANOVA has one independent variable, while a two-way ANOVA has two.
One-way ANOVA: Testing the relationship between shoe brand (Nike, Adidas, Saucony, Hoka) and race finish times in a marathon.
Two-way ANOVA: Testing the relationship between shoe brand (Nike, Adidas, Saucony, Hoka), runner age group (junior, senior, master’s), and race finishing times in a marathon.
All ANOVAs are designed to test for differences among three or more groups. If you are only testing for a difference between two groups, use a t-test instead.
What is multiple linear regression?: Multiple linear regression is a regression model that estimates the relationship between a quantitative dependent variable and two or more independent variables using a straight line.
How is the error calculated in a linear regression model?: Linear regression most often uses mean-square error (MSE) to calculate the error of the model. MSE is calculated by:
measuring the distance of the observed y-values from the predicted y-values at each value of x;
squaring each of these distances;
calculating the mean of each of the squared distances.
Linear regression fits a line to the data by finding the regression coefficient that results in the smallest MSE.
What is simple linear regression?: Simple linear regression is a regression model that estimates the relationship between one independent variable and one dependent variable using a straight line. Both variables should be quantitative.
For example, the relationship between temperature and the expansion of mercury in a thermometer can be modeled using a straight line: as temperature increases, the mercury expands. This linear relationship is so certain that we can use mercury thermometers to measure temperature.
What is a regression model?: A regression model is a statistical model that estimates the relationship between one dependent variable and one or more independent variables using a line (or a plane in the case of two or more independent variables).
A regression model can be used when the dependent variable is quantitative, except in the case of logistic regression, where the dependent variable is binary.
Where does the literature review go in a dissertation?: The literature review usually comes near the beginning of your thesis or dissertation. After the introduction, it grounds your research in a scholarly field and leads directly to your theoretical framework or methodology.
What is the purpose of a literature review?: There are several reasons to conduct a literature review at the beginning of a research project:
To familiarize yourself with the current state of knowledge on your topic
To ensure that you’re not just repeating what others have already done
To identify gaps in knowledge and unresolved problems that your research can address
To develop your theoretical framework and methodology
To provide an overview of the key findings and debates on the topic
Writing the literature review shows your reader how your work relates to existing research and what new insights it will contribute.
What is a literature review?: A literature review is a survey of scholarly sources (such as books, journal articles, and theses) related to a specific topic or research question.
It is often written as part of a thesis, dissertation, or research paper, in order to situate your work in relation to existing knowledge.
How should I organize a graduate school resume?: The sections in your graduate school resume depend on two things: your experience, and the focus of the program you’re applying to.
Always start with your education. If you have more than one degree, list the most recent one first.
The title and order of the other sections depend on what you want to emphasize. You might include things like:
Professional experience
Voluntary and extracurricular activities
Publications
Awards and honors
Skills and certifications
The resume should aim for a balance between two things: giving a snapshot of what you’ve done with your life so far, and showing that you’re a good candidate for graduate study.
What’s the difference between a resume and a CV?: A resume is typically shorter than a CV, giving only the most relevant professional and educational highlights.
An academic CV should give full details of your education and career, including lists of publications and presentations, certifications, memberships, grants, and research projects. Because it is more comprehensive, it’s acceptable for an academic CV to be many pages long.
Note that, outside of the US, resume and CV are often used interchangeably.
Should high school education be included in a grad school resume?: No, don’t include your high school courses and grades. The education section should only detail your college education.
If you want to discuss aspects of high school in your graduate school application, you can include this in your personal statement.
How long is a graduate school resume?: A resume for a graduate school application is typically no more than 1–2 pages long.
Note, however, that if you are asked to submit a CV (curriculum vitae), you should give comprehensive details of all your academic experience. An academic CV can be much longer than a normal resume.
Always carefully check the instructions and adhere to any length requirements for each application.
Can I use a t-test to measure the difference among several groups?: A t-test should not be used to measure differences among more than two groups, because the error structure for a t-test will underestimate the actual error when many groups are being compared.
If you want to compare the means of several groups at once, it’s best to use another statistical test such as ANOVA or a post-hoc test.
What is the difference between a one-sample t-test and a paired t-test?: A one-sample t-test is used to compare a single population to a standard value (for example, to determine whether the average lifespan of a specific town is different from the country average).
A paired t-test is used to compare a single population before and after some experimental intervention or at two different points in time (for example, measuring student performance on a test before and after being taught the material).
What does a t-test measure?: A t-test measures the difference in group means divided by the pooled standard error of the two group means.
In this way, it calculates a number (the t-value) illustrating the magnitude of the difference between the two group means being compared, and estimates the likelihood that this difference exists purely by chance (p-value).
Which t-test should I use?: Your choice of t-test depends on whether you are studying one group or two groups, and whether you care about the direction of the difference in group means.
If you are studying one group, use a paired t-test to compare the group mean over time or after an intervention, or use a one-sample t-test to compare the group mean to a standard value. If you are studying two groups, use a two-sample t-test.
If you want to know only whether a difference exists, use a two-tailed test. If you want to know if one group mean is greater or less than the other, use a left-tailed or right-tailed one-tailed test.
What is a t-test?: A t-test is a statistical test that compares the means of two samples. It is used in hypothesis testing, with a null hypothesis that the difference in group means is zero and an alternate hypothesis that the difference in group means is different from zero.
Who uses the MLA citation style?: MLA Style is the second most used citation style (after APA). It is mainly used by students and researchers in humanities fields such as literature, languages, and philosophy.
What should I do when source information is missing?: If information about your source is not available, you can either leave it out of the MLA citation or replace it with something else, depending on the type of information.
The most common scenarios (and what to do) are:
No author: Start with the source title.
No title: Provide a description of the source.
No date: Provide the date you accessed the information.
What is the basic structure of an MLA citation?: A standard MLA Works Cited entry is structured as follows:
Author. “Title of the Source.” Title of the Container, Other contributors, Version, Number, Publisher, Publication date, Location.
Only relevant information is included in the reference.
What is mixed-methods research?: In mixed-methods research, you use both qualitative and quantitative data collection and analysis methods to answer your research question.
How do I decide which research methods to use?: The research methods you use depend on the type of data you need to answer your research question.
If you want to measure something or test a hypothesis, use quantitative methods. If you want to explore ideas, thoughts and meanings, use qualitative methods.
If you want to analyze a large amount of readily-available data, use secondary data. If you want data specific to your purposes with control over how it is generated, collect primary data.
If you want to establish cause-and-effect relationships between variables, use experimental methods. If you want to understand the characteristics of a research subject, use descriptive methods.
What is statistical significance?: Statistical significance occurs when an observed pattern in the data is unlikely to have happened by chance (i.e. it falls outside of the range of values predicted by the null hypothesis).
Significance is usually denoted by a probability value (p-value). When this falls below a certain alpha value, then we say the result of the test is statistically significant. The alpha value is often set at 0.05 – that is, when there is a less than 5% probability that the result could have happened by chance.
What is a test statistic?: A test statistic is a number calculated by a statistical test. It describes how far your observed data is from the null hypothesis of no relationship between variables or no difference among sample groups.
The test statistic tells you how different two or more groups are from the overall population mean, or how different a linear slope is from the slope predicted by a null hypothesis. Different test statistics are used in different statistical tests.
What are the main assumptions of statistical tests?: Statistical tests commonly assume that:
the data are normally distributed
the groups that are being compared have similar variance
the data are independent
If your data does not meet these assumptions you might still be able to use a nonparametric statistical test, which have fewer requirements but also make weaker inferences.
Can you cite sources in an abstract?: Avoid citing sources in your abstract. There are two reasons for this:
The abstract should focus on your original research, not on the work of others.
The abstract should be self-contained and fully understandable without reference to other sources.
There are some circumstances where you might need to mention other sources in an abstract: for example, if your research responds directly to another study or focuses on the work of a single theorist. In general, though, don’t include citations unless absolutely necessary.
What is the purpose of an abstract?: An abstract is a concise summary of an academic text (such as a journal article or dissertation). It serves two main purposes:
To help potential readers determine the relevance of your paper for their own research.
To communicate your key findings to those who don’t have time to read the whole paper.
Abstracts are often indexed along with keywords on academic databases, so they make your work more easily findable. Since the abstract is the first thing any reader sees, it’s important that it clearly and accurately summarizes the contents of your paper.
Where does the abstract go in an APA paper?: The abstract comes after the title page and before the introduction in an APA format paper.
If you are writing a longer text (such as a thesis or dissertation), place the abstract after the acknowledgements and before the table of contents.
How long should an APA abstract be?: The APA manual suggests that most abstracts are around 150–250 words long. However, the length of an abstract varies depending on the publication or university. Always check the requirements, and don’t exceed the specified word count.
Are titles capitalized in MLA?: Yes. MLA Style uses title case, which means that all principal words (nouns, pronouns, verbs, adjectives, adverbs, and some conjunctions) are capitalized.
This applies to titles of sources as well as the title in the heading of your paper. Use MLA capitalization style even when the original source title uses different capitalization.
Do you italicize article titles in MLA?: The title of an article is not italicized in MLA style, but placed in quotation marks. This applies to articles from journals, newspapers, websites, or any other publication. Use italics for the title of the source where the article was published. For example:
“A Complete Guide to MLA Citation” is published on the Scribbr website.
Use the same formatting in the Works Cited entry and when referring to the article in the text itself.
How do you write a book title in MLA?: In MLA style, book titles appear in italics, with all major words capitalized. If there is a subtitle, separate it from the main title with a colon and a space. For example:
Dreams from My Father: A Story of Race and Inheritance
The format is the same in the Works Cited list and in the text itself. However, when you mention the book title in the text, you don’t have to include the subtitle.
The title of a part of a book – such as a chapter, short story or poem in a collection – is not italicized, but instead placed in quotation marks.
How do I find the DOI of an article?: The DOI is usually clearly visible when you open a journal article on an academic database. It is often listed near the publication date, and includes “doi.org” or “DOI:”. If the database has a “cite this article” button, this should also produce a citation with the DOI included.
If you can’t find the DOI, you can search on Crossref using information like the author, the article title, and the journal name.
How do I format a DOI in MLA style?: In MLA style citations, format DOIs with the prefix doi: followed by the string of letters and numbers.
doi:10.1177/0269881118806297
DOIs are used mainly when citing journal articles in MLA.
Why are DOIs important?: A DOI is a unique identifier for a digital document. DOIs are important in academic citation because they are more permanent than URLs, ensuring that your reader can reliably locate the source.
Journal articles and ebooks can often be found on multiple different websites and databases. The URL of the page where an article is hosted can be changed or removed over time, but a DOI is linked to the specific document and never changes.
What is a confounding variable?: A confounding variable, also called a confounder or confounding factor, is a third variable in a study examining a potential cause-and-effect relationship.
A confounding variable is related to both the supposed cause and the supposed effect of the study. It can be difficult to separate the true effect of the independent variable from the effect of the confounding variable.
In your research design, it’s important to identify potential confounding variables and plan how you will reduce their impact.
What is the difference between discrete and continuous variables?: Discrete and continuous variables are two types of quantitative variables:
Discrete variables represent counts (e.g. the number of objects in a collection).
Continuous variables represent measurable amounts (e.g. water volume or weight).
What is the difference between quantitative and categorical variables?: Quantitative variables are any variables where the data represent amounts (e.g. height, weight, or age).
Categorical variables are any variables where the data represent groups. This includes rankings (e.g. finishing places in a race), classifications (e.g. brands of cereal), and binary outcomes (e.g. coin flips).
You need to know what type of variables you are working with to choose the right statistical test for your data and interpret your results.
What are independent and dependent variables?: You can think of independent and dependent variables in terms of cause and effect: an independent variable is the variable you think is the cause, while a dependent variable is the effect.
In an experiment, you manipulate the independent variable and measure the outcome in the dependent variable. For example, in an experiment about the effect of nutrients on crop growth:
The independent variable is the amount of nutrients added to the crop field.
The dependent variable is the biomass of the crops at harvest time.
Defining your variables, and deciding how you will manipulate and measure them, is an important part of experimental design.
What is the most recent edition of the MLA Handbook?: The MLA Handbook is currently in its 8th edition, published in 2016.
This quick guide to MLA style explains the latest guidelines for citing sources and formatting papers according to MLA.
What is the easiest way to create MLA citations?: The fastest and most accurate way to create MLA citations is by using Scribbr’s MLA Citation Generator.
Search by book title, page URL or journal DOI to automatically generate flawless citations, or cite manually using the simple citation forms.
What font and size is used in MLA format?: MLA recommends using 12 point Times New Roman since it’s easy to read and installed on every computer. Other standard fonts such as Arial or Georgia are also acceptable. If in doubt, check with your supervisor which font you should be using.
What is experimental design?: Experimental design means planning a set of procedures to investigate a relationship between variables. To design a controlled experiment, you need:
A testable hypothesis
At least one independent variable that can be precisely manipulated
At least one dependent variable that can be precisely measured
When designing the experiment, you decide:
How you will manipulate the variable(s)
How you will control for any potential confounding variables
How many subjects or samples will be included in the study
How subjects will be assigned to treatment levels
Experimental design is essential to the internal and external validity of your experiment.
What is the difference between internal and external validity?: Internal validity is the degree of confidence that the causal relationship you are testing is not influenced by other factors or variables.
External validity is the extent to which your results can be generalized to other contexts.
The validity of your experiment depends on your experimental design.
What types of source are cited as a personal communication in APA Style?: In APA Style, all sources that are not retrievable for the reader are cited as personal communications. In other words, if your source is private or inaccessible to the audience of your paper, it’s a personal communication.
Common examples include conversations, emails, messages, letters, and unrecorded interviews or performances.
Should interviews be included in an APA reference list?: Interviews you conducted yourself are not included in your reference list, but instead cited in the text as personal communications.
Published or recorded interviews are included in the reference list. Cite them in the usual format of the source type (for example, a newspaper article, website or YouTube video).
How do I cite social media content in APA Style?: To cite a public post from social media, use the first 20 words of the post as a title, include the date it was posted and a URL, and mention the author’s username if they have one:
Dorsey, J. [@jack]. (2018, March 1). We’re committing Twitter to help increase the collective health, openness, and civility of public conversation, and to hold ourselves publicly [Tweet]. Twitter. https://twitter.com/jack/status/969234275420655616
To cite content from social media that is not publicly accessible (e.g. direct messages, posts from private groups or user profiles), cite it as a personal communication in the text, but do not include it in the reference list:
When contacted online, the minister stated that the project was proceeding “according to plan” (R. James, Twitter direct message, March 25, 2017).
How do I cite a source with no author in APA?: When no individual author name is listed, but the source can clearly be attributed to a specific organization – for example, a press release by a charity, a report by an agency, or a page from a company’s website – use the organization’s name as the author in your reference list and in-text citations.
When no author at all can be determined – for example, a collaboratively-edited wiki or an online article published anonymously – use the title in place of the author. In the in-text citation, put the title in quotation marks and shorten it if necessary.
When should I include an access date in an APA citation?: APA style usually does not require an access date. You never need to include one when citing journal articles, e-books, or other stable online sources.
However, if you are citing a website or online article that’s likely to change over time, it’s a good idea to include an access date. In this case, place the month, day, and year directly after the word “Retrieved”, and before the URL.
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Each plagiarism checker in this list has been tested to assess how accurately it can detect similarities and to analyze what kind of databases (e.g. websites, scholarly articles, books) your document is compared with. Check out the test results.
What is the most current edition of the APA manual?: The 7th edition APA Manual, published in October 2019, is the most current edition. However, the 6th edition, published in 2009, is still used by many universities and journals.
Where can I buy or download the APA Manual 7th edition?: The APA Manual 7th edition can be purchased at Amazon as a hardcover, paperback or spiral-bound version. You can also buy an ebook version at RedShelf.
When will people start using the 7th edition APA Manual?: The American Psychological Association anticipates that most people will start using the 7th edition in the spring of 2020 or thereafter.
It’s best to ask your supervisor or check the website of the journal you want to publish in to see which APA guidelines you should follow.
When should I include the edition in an APA book citation?: If you’re citing from an edition other than the first (e.g. a 2nd edition or revised edition), the edition is abbreviated in parentheses after the book’s title (e.g. 2nd ed. or rev. ed.).
Do I need to include the publisher’s location in an APA book citation?: The 6th edition of the APA manual requires you to include the publisher’s location when you cite from a print book. The city and state should be included for US-based publishers, the city and country for publishers anywhere else.
If you are following the 7th edition, just write the name of the publisher – no location information is required.
When should I cite a chapter instead of the whole book?: In APA, MLA and Chicago Style, when the book’s chapters are written by different authors, you should cite the specific chapter you are referring to.
Single-author books should be cited as a whole, even if you only quote or paraphrase from one chapter.
Should I include the exact publication date or just the year in an APA journal citation?: In an APA reference list, journal article citations include only the year of publication, not the exact date, month, or season.
The inclusion of volume and issue numbers makes a more specific date unnecessary.
When should I include a DOI or URL in an APA journal citation?: In an APA journal citation, if a DOI (digital object identifier) is available for an article, always include it.
If an article has no DOI, and you accessed it through a database or in print, just omit the DOI.
If an article has no DOI, and you accessed it through a website other than a database (for example, the journal’s own website), include a URL linking to the article.
How many authors do I include in an APA reference list entry?: The APA 6th edition recommends including the names of up to seven authors in a reference list entry. When an article has more than seven authors, replace the names prior to the final listed author with an ellipsis, but do not omit the final author:
Davis, Y., Smith, J., Caulfield, F., Pullman, H., Carlisle, J., Donahue, S. D., … O’Brien, T. (2012).
Note that the 7th edition of the APA manual, published in 2019, recommends including up to 20 authors in a reference list entry.
How do I format a DOI in APA style?: In your reference list entry for a journal article or other online source, APA currently recommends writing the full DOI address that gives access to the article. For example:
https://doi.org/10.1037/rev0000126
The old guidelines were to present DOIs by writing “doi:” followed by the numerical string. For example:
doi:10.1037/rev0000126
If you’re following the 6th edition, this format is still accepted, as long as it’s used consistently.
What’s the difference between reliability and validity?: Reliability and validity are both about how well a method measures something:
Reliability refers to the consistency of a measure (whether the results can be reproduced under the same conditions).
Validity refers to the accuracy of a measure (whether the results really do represent what they are supposed to measure).
If you are doing experimental research, you also have to consider the internal and external validity of your experiment.
What is sampling?: A sample is a subset of individuals from a larger population. Sampling means selecting the group that you will actually collect data from in your research. For example, if you are researching the opinions of students in your university, you could survey a sample of 100 students.
In statistics, sampling allows you to test a hypothesis about the characteristics of a population.
What’s the difference between quantitative and qualitative methods?: Quantitative research deals with numbers and statistics, while qualitative research deals with words and meanings. Each is associated with a range of research methods.
Quantitative methods allow you to test a hypothesis by systematically collecting and analyzing data. Common methods include experiments, observations recorded as numbers, and surveys with closed-ended questions.
Qualitative methods allow you to explore ideas and experiences in depth. Common methods include interviews with open-ended questions, observations described in words, and literature reviews that explore concepts and theories.
Qualitative methods tend to be more flexible, while quantitative methods are more reproducible.
Where does the methodology section go in a research paper?: In a scientific paper, the methodology always comes after the introduction and before the results, discussion and conclusion. The same basic structure also applies to a thesis, dissertation, or research proposal.
Depending on the length and type of document, you might also include a literature review or theoretical framework before the methodology.
What’s the difference between method and methodology?: Methodology refers to the overarching strategy and rationale of your research project. It involves studying the methods used in your field and the theories or principles behind them, in order to develop an approach that matches your objectives.
Methods are the specific tools and procedures you use to collect and analyze data (for example, experiments, surveys, and statistical tests).
In shorter scientific papers, where the aim is to report the findings of a specific study, you might simply describe what you did in a methods section.
In a longer or more complex research project, such as a thesis or dissertation, you will probably include a methodology section, where you explain your approach to answering the research questions and cite relevant sources to support your choice of methods.
Can I submit the same personal statement with every application?: If you’re applying to multiple graduate school programs, you should tailor your personal statement to each application.
Some applications provide a prompt or question. In this case, you might have to write a new personal statement from scratch: the most important task is to respond to what you have been asked.
If there’s no prompt or guidelines, you can re-use the same idea for your personal statement – but change the details wherever relevant, making sure to emphasize why you’re applying to this specific program.
If the application also includes other essays, such as a statement of purpose, you might have to revise your personal statement to avoid repeating the same information.
How long is a personal statement?: The typical length of a personal statement for graduate school applications is between 500 and 1,000 words.
Different programs have different requirements, so always check if there’s a minimum or maximum length and stick to the guidelines. If there is no recommended word count, aim for no more than 1-2 pages.
What’s the difference between a personal statement and a statement of purpose?: A statement of purpose is usually more formal, focusing on your academic or professional goals. It shouldn’t include anything that isn’t directly relevant to the application.
A personal statement can often be more creative. It might tell a story that isn’t directly related to the application, but that shows something about your personality, values, and motivations.
However, both types of document have the same overall goal: to demonstrate your potential as a graduate student and show why you’re a great match for the program.
What font should I use in a Chicago style paper?: Chicago format doesn’t require you to use any specific font, as long as you choose something readable. A good standard choice is 12 pt Times New Roman.
What is the difference between a reference list and a bibliography?: A reference list is used with Chicago author-date citations.
A bibliography is used with Chicago footnote citations.
Both present the exact same information – the only difference is the placement of the year in source citations:
In a reference list entry, the publication year appears directly after the author’s name.
In a bibliography entry, the year appears near the end of the entry (the exact placement depends on the source type).
There are also other types of bibliography that work as stand-alone texts, such as an annotated bibliography.
What is Turabian style?: Turabian style is a version of Chicago style designed specifically for students and researchers. It follows most Chicago conventions, but also adds extra guidelines for formatting research papers, theses and dissertations.
More information can be found in A Manual for Writers of Research Papers, Theses, and Dissertations by Kate L. Turabian, now in its ninth edition.
What is the difference between footnotes and endnotes?: Footnotes appear at the bottom of the relevant page. Endnotes appear in a list at the end of the text, just before the bibliography.
Chicago note citations follow the exact same format whether they appear in footnotes or endnotes.
Do I have to include a bibliography or reference list?: In Chicago author-date style, your text must include a reference list. It appears at the end of your paper and gives full details of every source you cited.
In notes and bibliography style, you use Chicago style footnotes to cite sources; a bibliography is optional but recommended. If you don’t include one, be sure to use a full note for the first citation of each source.
Should I use short notes or full notes?: If your text includes a Chicago style bibliography, you only ever need to use short notes. Each short note must correspond to a bibliography entry.
If you do not include a bibliography, your first citation of each source should be a full note, while all subsequent citations should be short notes.
When should I use “et al.” in Chicago citations?: When a source has four or more authors, your in-text citation or footnote should give only the first author’s name followed by “et al.” (Latin for “and others”). This makes your citations more concise.
In your bibliography or reference list, when a source has more than 10 authors, list the first seven followed by “et al.”
When should I include page numbers in Chicago style citations?: Page numbers should be included in your Chicago in-text citations when:
You’re quoting from the text.
You’re paraphrasing a particular passage.
You’re referring to information from a specific section.
When you’re referring to the overall argument or general content of a source, it’s unnecessary to include page numbers.
How are block quotes formatted in MLA?: To format a block quote in MLA:
Introduce the quote with a colon and set it on a new line.
Indent the whole quote 0.5 inches from the left margin.
Place the MLA in-text citation after the period at the end of the block quote.
Then continue your text on a new line (not indented).
How long is a block quote in MLA?: In MLA style, if you quote more than four lines from a source, use MLA block quote formatting.
If you are quoting poetry, use block quote formatting for any quote longer than three lines.
How do I cite a poem in the text in MLA?: An MLA in-text citation should always include the author’s last name, either in the introductory text or in parentheses after a quote.
If line numbers or page numbers are included in the original source, add these to the citation.
If you are discussing multiple poems by the same author, make sure to also mention the title of the poem (shortened if necessary). The title goes in quotation marks.
How do I cite a poem in an MLA Works Cited list?: In the list of Works Cited, start with the poet’s name and the poem’s title in quotation marks. The rest of the citation depends on where the poem was published.
If you read the poem in a book or anthology, follow the format of an MLA book chapter citation. If you accessed the poem online, follow the format of an MLA website citation.
Should I include line numbers in an MLA poetry citation?: Only use line numbers in an MLA in-text citation if the lines are numbered in the original source. If so, write “lines” in the first citation of the poem, and only the numbers in subsequent citations.
If there are no line numbers in the source, you can use page numbers instead. If the poem appears on only one page of a book (or on a website), don’t include a number in the citation.
How do I format a poetry quotation in MLA?: To quote poetry in MLA style, introduce the quote and use quotation marks as you would for any other source quotation.
If the quote includes line breaks, mark these using a forward slash with a space on either side. Use two slashes to indicate a stanza break.
If the quote is longer than three lines, set them off from the main text as an MLA block quote. Reproduce the line breaks, punctuation and formatting of the original.
What does an APA in-text citation for a website look like?: When citing an entire website or online article in APA Style, the in-text citation consists of the author’s last name and year of publication. For example: (Worland & Williams, 2015).
Note that the author can also be an organization. For example: (American Psychological Association, 2019).
Since web pages don’t have page numbers, you don’t include a locator in the in-text citation.
When should I include a page number in the in-text citation?: Always include page numbers in the APA in-text citation when quoting a source. Don’t include page numbers when referring to a work as a whole – for example, an entire book or journal article.
What should I do when the author or publication date is unknown?: No author
Instead of the author’s name, include the first few words of the work’s title in the in-text citation. Enclose the title in double quotation marks when citing an article, web page or book chapter. Italicize the title of periodicals, books, and reports.
No publication date
If the publication date is unknown, use “n.d.” (no date) instead. For example: (Johnson, n.d.).
When should I use “et al.” in APA in-text citations?: Depending on the number of authors a source has, an APA in-text citation is shortened by using “et al.” (meaning “and others”) after the first author’s name.
Sources with 3–5 authors are written in full the first time and shortened from the second citation onwards. Sources with 6+ authors are always shortened, even the first time.
First in-text citation: (Taylor, Kotler, Johnson, & Parker, 2018)
Subsequent in-text citation: (Taylor et al., 2018)
How can I get better at proofreading?: Whether you’re publishing a blog, submitting a research paper, or even just writing an important email, there are a few techniques you can use to make sure it’s error-free:
Take a break: Set your work aside for at least a few hours so that you can look at it with fresh eyes.
Proofread a printout: Staring at a screen for too long can cause fatigue – sit down with a pen and paper to check the final version.
Use digital shortcuts: Take note of any recurring mistakes (for example, misspelling a particular word, switching between US and UK English, or inconsistently capitalizing a term), and use Find and Replace to fix it throughout the document.
If you want to be confident that an important text is error-free, it might be worth choosing a professional proofreading service instead.
What is the difference between proofreading and editing?: Editing and proofreading are different steps in the process of revising a text.
Editing comes first, and can involve major changes to content, structure and language. The first stages of editing are often done by authors themselves, while a professional editor makes the final improvements to grammar and style (for example, by improving sentence structure and word choice).
Proofreading is the final stage of checking a text before it is published or shared. It focuses on correcting minor errors and inconsistencies (for example, in punctuation and capitalization). Proofreaders often also check for formatting issues, especially in print publishing.
How much does professional proofreading cost?: The cost of proofreading depends on the type and length of text, the turnaround time, and the level of services required. Most proofreading companies charge per word or page, while freelancers sometimes charge an hourly rate.
For proofreading alone, which involves only basic corrections of typos and formatting mistakes, you might pay as little as $0.01 per word, but in many cases, your text will also require some level of editing, which costs slightly more.
It’s often possible to purchase combined proofreading and editing services and calculate the price in advance based on your requirements.
What qualifications do you need to become a proofreader?: There are many different routes to becoming a professional proofreader or editor. The necessary qualifications depend on the field – to be an academic or scientific proofreader, for example, you will need at least a university degree in a relevant subject.
For most proofreading jobs, experience and demonstrated skills are more important than specific qualifications. Often your skills will be tested as part of the application process.
To learn practical proofreading skills, you can choose to take a course with a professional organization such as the Society for Editors and Proofreaders. Alternatively, you can apply to companies that offer specialized on-the-job training programmes, such as the Scribbr Academy.
Is a newspaper article a primary or secondary source?: Articles in newspapers and magazines can be primary or secondary depending on the focus of your research.
In historical studies, old articles are used as primary sources that give direct evidence about the time period. In social and communication studies, articles are used as primary sources to analyze language and social relations (for example, by conducting content analysis or discourse analysis).
If you are not analyzing the article itself, but only using it for background information or facts about your topic, then the article is a secondary source.
Is a movie a primary or secondary source?: A fictional movie is usually a primary source. A documentary can be either primary or secondary depending on the context.
If you are directly analyzing some aspect of the movie itself – for example, the cinematography, narrative techniques, or social context – the movie is a primary source.
If you use the movie for background information or analysis about your topic – for example, to learn about a historical event or a scientific discovery – the movie is a secondary source.
Whether it’s primary or secondary, always properly cite the movie in the citation style you are using. Learn how to create an MLA movie citation or an APA movie citation.
How can you tell if a source is primary or secondary?: To determine if a source is primary or secondary, ask yourself:
Was the source created by someone directly involved in the events you’re studying (primary), or by another researcher (secondary)?
Does the source provide original information (primary), or does it summarize information from other sources (secondary)?
Are you directly analyzing the source itself (primary), or only using it for background information (secondary)?
Some types of source are nearly always primary: works of art and literature, raw statistical data, official documents and records, and personal communications (e.g. letters, interviews). If you use one of these in your research, it is probably a primary source.
Always make sure to properly cite your sources to avoid plagiarism.
What are some examples of secondary sources?: Common examples of secondary sources include academic books, journal articles, reviews, essays, and textbooks.
Anything that summarizes, evaluates or interprets primary sources can be a secondary source. If a source gives you an overview of background information or presents another researcher’s ideas on your topic, it is probably a secondary source.
What are some examples of primary sources?: Common examples of primary sources include interview transcripts, photographs, novels, paintings, films, historical documents, and official statistics.
Anything you directly analyze or use as first-hand evidence can be a primary source, including qualitative or quantitative data that you collected yourself.
What font and font size is used in APA format?: The American Psychological Association (APA) recommends the use of Times New Roman, size 12.
The same font and font size is used for the throughout the whole document, including the running head, page numbers, headings and the reference page.
How do I set up APA format in Word?: The easiest way to set up APA format in Word is to download Scribbr’s APA format Word template. This will make sure that:
One-inch page margins are set.
APA heading styles are imported.
A running head and page numbers are included in the header.
The font size and line spacing is correct.
In addition, you’ll have an easy-to-follow structure with examples and useful links to more information.
Download the APA format Word Template
How do I cite in APA format?: There are many guidelines and exceptions when citing sources in APA format. The easiest and most effective way of citing in APA format is by using Scribbr’s free APA Citation Generator. This is how it works:
Automatically retrieve all required information by entering a page URL, journal article DOI or book ISBN.
Check the retrieved information and make changes if necessary.
Click on ‘Generate citation’.
Copy the APA reference entry and in-text citation.
Generate APA citations
Who uses APA format?: APA is a publication manual widely used by professionals, researchers and students in the social and behavioural sciences, including fields like education, psychology, and business.
Be sure to check the guidelines of your university or the journal you want to be published in before applying APA format.
Should I include page numbers on the title and reference page?: Yes, page numbers are included on all pages, including the title page, table of contents and reference page. To insert page numbers in Microsoft Word, click ‘Insert’ and then ‘Page number’.
Page numbers should be right aligned in the header (top of the page). Don’t forget to set the font to Times New Roman, size 12.
See an example of an APA header
Should I check my paper for plagiarism before submitting it to my instructor?: If you’ve correctly cited all the sources you used, then you do not need to use a plagiarism checker before submitting your paper to your instructor. However, if you want to be sure that you didn’t forget to cite anything, then you can use a plagiarism checker yourself.
There are both free plagiarism checkers and paid plagiarism checkers, such as the Scribbr Plagiarism Checker.
To help you, we compared popular plagiarism checkers to find out which one is best.
Best plagiarism checker comparison
Can you plagiarize yourself?: Although it sounds contradictory, you can indeed plagiarize yourself. This is called self-plagiarism. Self-plagiarism goes against the expectations of the reader that the paper you submitted is new.
You can plagiarize yourself by, for instance:
Submitting a document you previously submitted for a different course
Using a section of a previous paper without correctly citing yourself as the source
Although self-plagiarism is often unintentional, it can have serious consequences. Be sure to cite your previous work or discuss the decision to use your old paper with your professor.
Read more about self-plagiarism
Is paraphrasing considered plagiarism?: Paraphrasing without crediting the original author is considered plagiarism and therefore has serious consequences.
However, if you do credit the original author correctly using an in-text citation or footnote citation and include the full source in the reference list, then you do not commit plagiarism.
In order to avoid plagiarism, you must always cite the source in the correct citation format; otherwise, you are presenting something as your own work, even though it’s not.
The difference between paraphrasing and plagiarism
What is the difference between plagiarism and paraphrasing?: Plagiarism is the act of using someone else’s work or ideas without crediting the original author and thereby pretending it’s your own.
Paraphrasing means rephrasing the original text in your own words.
So, where does the confusion come from?
When using someone else’s work, you can either quote or paraphrase it to prevent plagiarism. Paraphrase a text if you want to clarify or shorten the original text. Quote the text if you want to keep the exact wording and meaning of the original source.
Is it plagiarism if you cite the source?: If you correctly cite the source you do not commit plagiarism. However, the word ‘correct’ is vital in this sentence. In order to avoid plagiarism you must adhere to the guidelines of your citation style (e.g. APA citation style or MLA citation style).
Plagiarism checker software can be used to check your text for plagiarism. This software compares your text with billions of webpages, books and articles.
Scribbr Plagiarism Checker
Are plagiarism checkers accurate?: The accuracy depends on the plagiarism checker you use. Scribbr is the most accurate plagiarism checker. Many free plagiarism checkers fail to detect all plagiarism or falsely flag text as plagiarism.
Take a look at this comparison of free and paid plagiarism checkers for students to find the most accurate plagiarism checker.
The accuracy is determined by two factors: the algorithm (which recognizes the plagiarism) and the size of the database (with which your document is compared).
Size of the database
Many free plagiarism checkers only check your paper against websites – not against books, journals or papers previously submitted by other students. Therefore, these plagiarism checkers are not very accurate, as they miss a lot of plagiarism.
Algorithm
Most plagiarism checkers are only able to detect “direct plagiarism”, or instances where the sentences are exactly the same as in the original source. However, a good plagiarism checker is also able to detect “patchwork plagiarism” (sentences where some words are changed or synonyms are used).
What happens if you plagiarize?: The consequences of plagiarism vary depending on the severity of the infraction. Some types of plagiarism, such as direct plagiarism, are more serious than others, such as self-plagiarism.
If you’re a student, then you might fail the course, be suspended or expelled, or be obligated to attend a workshop on plagiarism. It depends on whether it’s your first offense or whether you’ve done it before.
As an academic or professional, the consequences are more serious. Aside from the fact that plagiarizing seriously damages your reputation, you might also lose your research funding and/ or your job.
Plagiarizing is a serious offense, and knowing how to avoid plagiarism is therefore important. Read more about the consequences of plagiarism and use a plagiarism checker to detect plagiarism yourself.

Number of authors	In-text citation	Works Cited entry
1 author	(Moore 37)	Moore, Jason W.
2 authors	(Moore and Patel 37)	Moore, Jason W., and Raj Patel.
3+ authors	(Moore et al. 37)	Moore, Jason W., et al.

Longitudinal study	Cross-sectional study
Repeated observations	Observations at a single point in time
Observes the same group multiple times	Observes different groups (a “cross-section”) in the population
Follows changes in participants over time	Provides snapshot of society at a given point