Chi-squared test

A chi-squared test, also called a chi-square or χ2 test, is a statistical hypothesis test used to analyze contingency tables, particularly when sample sizes are large. It commonly examines whether two categorical variables are independent. Pearson's chi-squared test compares expected and observed frequencies across categories. The test statistic follows, or increasingly approximates, a chi-squared distribution under the null hypothesis. Fisher's exact test is used instead for contingency tables with smaller samples.

Type

Statistical hypothesis test

Main use

Testing independence of two categorical variables

Small-sample alternative

Fisher's exact test