How to report numbers and statistics in APA style

The APA style guide is commonly used for reporting research results in the social and natural sciences. This article walks you through APA style standards for reporting statistics in academic writing.

Statistical analysis involves gathering and testing quantitative data to make inferences about the world. A statistic is any number that describes a sample: it can be a proportion, a range, or a measurement, and so on.

When reporting statistics, use these formatting rules and suggestions from the APA style guide where relevant.

Numbers and measurements

In general, the APA advises using words for numbers under 10 and numerals for 10 and greater.

You should always use numerals for:

  • exact numbers before units of measurement or time
  • mathematical equations
  • percentages and percentiles
  • ratios, decimals, and uncommon fractions
  • scores and points on scales (e.g., 7-point scale)
  • exact amounts of money.

Units of measurement and time

Report exact measurements using numerals, and use symbols or abbreviations for common units of measurement when they accompany exact measurements. Include a space between the number and the abbreviation.

When stating approximate figures, use words to express numbers under 10, and spell out the names of units of measurement.

Examples: Reporting exact and approximate figures
  • The ball weighed 7 kg.
  • The ball weighed approximately seven kilograms.

Measurements should be reported in metric units. If you recorded measurements in non-metric units, include metric equivalents in your report as well as the original units.

Percentages

Use numerals for percentages along with the percent symbol (%). Don’t insert a space between the number and the symbol.

Words for “percent” or “percentage” should only be used in text when numbers aren’t used.

Examples: Reporting percentages
  • 15% of respondents agreed with the statement.
  • The percentage was higher in 2020.

Decimal places and leading zeros

The number of decimal places to report depends on what you’re reporting. Generally, you should aim to round numbers while retaining precision. It’s best to present fewer decimal digits to aid easy understanding.

The following guidelines are usually applicable.

One decimal place Two decimal places
  • Correlation coefficients
  • Proportions
  • Inferential test statistics such as t values, F values, and chi-squares

Use two or three decimal places and report exact values for all p values greater than .001. For p values smaller than .001, report them as p < .001.

Leading zeros

A leading zero is zero before the decimal point for numbers less than one. In APA style, it’s only used in some cases.

Use a leading zero only when the statistic you’re describing can be greater than one. If it can never exceed one, omit the leading zero.

Use a leading zero Don’t use a leading zero
  • Variables that can be greater than 1 (e.g., height or weight)
  • Cohen’s d
  • t values
  • F value
  • z values
  • p values
  • Pearson’s correlation coefficient
  • Coefficient of determination
  • Cronbach’s alpha
Examples: Use of decimal places and leading zeros
  • Consumers reported high satisfaction with the services (M = 4.1, SD = 0.8).
  • The correlation was medium-sized (r = .35).
  • Although significant results were obtained, the effect was relatively small (p = .015, d = 0.11).

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Formatting mathematical formulas

Provide formulas only when you use new or uncommon equations. For short equations, present them within one line in the main text whenever possible.

Make the order of operations as clear as possible by using parentheses (round brackets) for the first step, brackets [square brackets] for the second step, and braces {curly brackets} for the third step, where necessary.

Example: Short mathematical formula
We used the formula c = [(x − 1)/b]-1 in our analysis.

More complex equations, or equations that take more than one line, should be displayed on their own lines. Equations should be displayed and numbered if you will reference them later on, regardless of their complexity. Number equations by placing the numbers in parentheses near the right of the page.

Example: Numbering mathematical formulas
Formatting equations in APA

Formatting statistical terms

When reporting statistical results, present information in easily understandable ways. You can use a mix of text, tables and figures to present data effectively when you have a lot of numbers to report.

In your main text, use helpful words like “respectively” or “in order”  to aid understanding when listing several statistics in a sequence.

The APA manual provides guidelines for dealing with statistical terms, symbols and abbreviations.

Symbols and abbreviations

Population parameters are often represented with Greek letters, while sample statistics are often represented with italicized Latin letters.

Use the population symbol (N) for the total number of elements in a sample, and use the sample symbol (n) for the number of elements in each subgroup of the full sample.

In general, abbreviations should be defined on first use, but this isn’t always the case for common statistical abbreviations.

Define Don’t define
  • Abbreviations that do not represent statistics: ANOVA, CI, CFA
  • Non-standard abbreviations that appear in tables and figures, even if they are already defined in the text.
  • Statistical symbols or abbreviations: M, SD, F, t, df, p, N, n, OR
  • Greek letters: α, β, χ2
Use symbols for statistical terms Use words for statistical terms
When directly referring to a numerical quantity or operator: M = 5.41 In the main text: “the mean accuracy was higher…”

Capitalization, italicization and hyphenation

Statistical terms such as t test, z test, and p value always begin with a lowercase, italicized letter. Never begin a sentence with lowercase statistical abbreviations.

These statistical terms should only be hyphenated when they modify a subsequent word (e.g., “z-test results” versus results of “z tests”).

You can form plurals of statistical symbols (e.g., M or p) by adding a non-italicized “s” to the end with no apostrophe (e.g., Ms or ps).

In general, the following guidelines apply.

Italicize Don’t italicize
  • Letters when they are statistical symbols or algebraic variables: Cohen’s d, SD, p value, t test
  • Greek letters: σ or χ2
  • Subscripts for statistical symbols: Mcontrol
  • Trigonometric terms: sin, cos
  • Vectors or matrices (boldface these instead): V, X 
Capitalize Don’t capitalize
Names of effects or variables only when they appear with multiplication signs: Age × Sex effect Lowercase statistical terms: t test, p value

Round vs square brackets

Always aim to avoid nested parentheses and brackets when reporting statistics. Instead, you should use commas to separate related statistics.

Use round brackets (parentheses) Use square brackets
  • Degrees of freedom
  • Statistical values when they aren’t already in parentheses
  • Confidence interval limits
  • Statistics in a text that’s already enclosed within parentheses
Examples: Reporting values in parentheses
  • Scores improved between the pretest and posttest (p <.001).
  • Significant differences in test scores were recorded, F(1, 30) = 4.67, p = .003.
  • (A previous meta-analysis highlighted low effect sizes [d = 0.1] in the field).

Reporting means and standard deviations

Report descriptive statistics to summarize your data. Quantitative data is often reported using means and standard deviations, while qualitative data (e.g., demographic variables) is reported using proportions.

Means and standard deviations can be presented in the main text and/or in parentheses. You don’t need to repeat the units of measurement (e.g., centimeters) for statistics relating to the same data.

Examples: Reporting mean and standard deviation
  • Average sample height was 136.4 cm (SD = 15.1).
  • The height of the initial sample was relatively low (M = 125.9 cm, SD = 16.6).
  • Height significantly varied between children aged 5–7, 8–10, and 11–13. The means were 115.3 cm, 133.5 cm, and 149.1 cm, respectively.

Reporting chi-square tests

To report the results of a chi-square test, include the following:

  • the degrees of freedom (df) in parentheses
  • the chi-square (χ2) value (also referred to as the chi-square test statistic)
  • the p value
Example: Reporting chi-square test results
  • A chi-square test of independence revealed a significant association between gender and product preference, χ2 (8) = 19.7, p = .012.
  • Based on a chi-square test of goodness of fit, χ2 (4) = 11.34, p = .023, the sample’s distribution of religious affiliations matched that of the population’s.

Reporting z tests and t tests

For z tests

To report the results of a z test, include the following:

  • the z value (also referred to as the z statistic or z score)
  • the p value
Example: Reporting z test results
  • The participants’ scores were higher than the population average, z = 2.48, p = .013.
  • Higher scores were obtained on the new 20-item scale compared to the previous 40-item scale, z = 2.67, p = .007.

For t tests

To report the results of a t test, include the following:

  • the degrees of freedom (df) in parentheses
  • the t value (also referred to as the t statistic)
  • the p value
Example: Reporting t test results
  • Older adults experienced significantly more loneliness than younger adults, t(32) = 2.94, p = .006.
  • Reaction times were significantly faster for mice in the experimental condition, t(53) = 5.94, p < .001.

Reporting analysis of variance (ANOVAs)

To report the results of an ANOVA, include the following:

  • the degrees of freedom (between groups, within groups) in parentheses
  • the F value (also referred to as the F statistic)
  • the p value
Example: Reporting ANOVA results
  • A one-way ANOVA demonstrated that the effect of leadership style was significant for employee engagement, F(2, 78) = 4.58, p = .013.
  • We found a statistically significant main effect of age group on social media use, F(3, 117) = 3.19, p = .026.

Reporting correlations

To report the results of a correlation, include the following:

  • the degrees of freedom in parentheses
  • the r value (the correlation coefficient)
  • the p value
Example: Reporting correlation results
  • We found a strong correlation between average temperature and new daily cases of COVID-19, r = .42, p < .001.

Reporting regressions

Results of regression analyses are often displayed in a table because the output includes many numbers.

To report the results of a regression analysis in the text, include the following:

  • the R2 value (the coefficient of determination)
  • the F value (also referred to as the F statistic)
  • the degrees of freedom in parentheses
  • the p value

The format is usually:

Example: Reporting regression results
  • SAT scores predicted college GPA, R2 = .34, F(1, 416) = 6.71, p = .009.

Reporting confidence intervals

You should report confidence intervals of effect sizes (e.g., Cohen’s d) or point estimates where relevant.

To report a confidence interval, state the confidence level and use brackets to enclose the lower and upper limits of the confidence interval, separated by a comma.

Example: Reporting confidence intervals
  • Older adults experienced significantly more loneliness than younger adults, t(32) = 2.94, p = .006, d = 0.81, 95% CI [0.6, 1.02].
  • On average, the treatment resulted in a 30% reduction in migraine frequency, 99% CI [26.5, 33.5].

When presenting multiple confidence intervals with the same confidence levels in a sequence, don’t repeat the confidence level or the word “CI.”

Frequently asked questions about APA style statistics

What statistical results do you need to report according to APA style?

According to the APA guidelines, you should report enough detail on inferential statistics so that your readers understand your analyses.

Report the following for each hypothesis test:

  • the test statistic value
  • the degrees of freedom
  • the exact p value (unless it is less than 0.001)
  • the magnitude and direction of the effect

You should also present confidence intervals and estimates of effect sizes where relevant.

How many decimal places do you use in APA style?

The number of decimal places to report depends on what you’re reporting. Generally, you should aim to round numbers while retaining precision. It’s best to present fewer decimal digits to aid easy understanding.

Use one decimal place for:

Use two decimal places for:

  • Correlation coefficients
  • Proportions
  • Inferential test statistics such as t values, F values, and chi-squares.
When should I use tables or figures to present numbers?

In APA style, statistics can be presented in the main text or as tables or figures. To decide how to present numbers, you can follow APA guidelines:

  • To present three or fewer numbers, try a sentence,
  • To present between 4 and 20 numbers, try a table,
  • To present more than 20 numbers, try a figure.

Since these are general guidelines, use your own judgment and feedback from others for effective presentation of numbers.

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Pritha Bhandari

Pritha has an academic background in English, psychology and cognitive neuroscience. As an interdisciplinary researcher, she enjoys writing articles explaining tricky research concepts for students and academics.

1 comment

Pritha Bhandari
Pritha Bhandari (Scribbr Team)
April 1, 2021 at 8:15 PM

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