## How to Find Degrees of Freedom | Definition & Formula

Degrees of freedom, often represented by v or df, is the number of independent pieces of information used to calculate a statistic. It’s calculated as the sample size minus the number of restrictions.

Degrees of freedom are normally reported in brackets beside the test statistic, alongside the results of the statistical test.

Continue reading: How to Find Degrees of Freedom | Definition & Formula

## Central Limit Theorem | Formula, Definition & Examples

The central limit theorem states that if you take sufficiently large samples from a population, the samples’ means will be normally distributed, even if the population isn’t normally distributed.

Continue reading: Central Limit Theorem | Formula, Definition & Examples

## What Is Kurtosis? | Definition, Examples & Formula

Kurtosis is a measure of the tailedness of a distribution. Tailedness is how often outliers occur. Excess kurtosis is the tailedness of a distribution relative to a normal distribution.

• Distributions with medium kurtosis (medium tails) are mesokurtic.
• Distributions with low kurtosis (thin tails) are platykurtic.
• Distributions with high kurtosis (fat tails) are leptokurtic.

Tails are the tapering ends on either side of a distribution. They represent the probability or frequency of values that are extremely high or low compared to the mean. In other words, tails represent how often outliers occur.

Example: Types of kurtosis Continue reading: What Is Kurtosis? | Definition, Examples & Formula

## Systematic Review | Definition, Example, & Guide

A systematic review is a type of review that uses repeatable methods to find, select, and synthesize all available evidence. It answers a clearly formulated research question and explicitly states the methods used to arrive at the answer.

Continue reading: Systematic Review | Definition, Example, & Guide

## Probability Distribution | Formula, Types, & Examples

A probability distribution is a mathematical function that describes the probability of different possible values of a variable. Probability distributions are often depicted using graphs or probability tables.

Common probability distributions include the binomial distribution, Poisson distribution, and uniform distribution. Certain types of probability distributions are used in hypothesis testing, including the standard normal distribution, the F distribution, and Student’s t distribution.

Continue reading: Probability Distribution | Formula, Types, & Examples

## Frequency Distribution | Tables, Types & Examples

A frequency distribution describes the number of observations for each possible value of a variable. Frequency distributions are depicted using graphs and frequency tables.

Continue reading: Frequency Distribution | Tables, Types & Examples

The chi-square (Χ2) distribution table is a reference table that lists chi-square critical values. A chi-square critical value is a threshold for statistical significance for certain hypothesis tests and defines confidence intervals for certain parameters.

Chi-square critical values are calculated from chi-square distributions. They’re difficult to calculate by hand, which is why most people use a reference table or statistical software instead.

## Chi-Square Test of Independence | Formula, Guide & Examples

A chi-square (Χ2) test of independence is a nonparametric hypothesis test. You can use it to test whether two categorical variables are related to each other.

Continue reading: Chi-Square Test of Independence | Formula, Guide & Examples

## Chi-Square Goodness of Fit Test | Formula, Guide & Examples

A chi-square (Χ2) goodness of fit test is a type of Pearson’s chi-square test. You can use it to test whether the observed distribution of a categorical variable differs from your expectations.

The chi-square goodness of fit test tells you how well a statistical model fits a set of observations. It’s often used to analyze genetic crosses.

Continue reading: Chi-Square Goodness of Fit Test | Formula, Guide & Examples

## Chi-Square (Χ²) Tests | Types, Formula & Examples

A Pearson’s chi-square test is a statistical test for categorical data. It is used to determine whether your data are significantly different from what you expected. There are two types of Pearson’s chi-square tests:

Chi-square is often written as Χ2 and is pronounced “kai-square” (rhymes with “eye-square”). It is also called chi-squared.

Continue reading: Chi-Square (Χ²) Tests | Types, Formula & Examples