Glossary items: click on the icon to go directly to the glossary entry


You should use a two-way Chi-square test when:

  • Dealing with the frequenciesglossary item: Frequency  classified according to two sets of categories in a contingency tableglossary item: Contingency table
  • Each item sampled contributes to only one cell in the contingency tableglossary item: Contingency table
  • Looking for a difference between an observed frequency distributionglossary item: observed frequency distribution  of a single sample and an expected frequency distributionglossary item: expected frequency distribution  based on no association between the two variables


Do not use this test when:

  • Using descriptive statisticsglossary item: descriptive statistics , percentagesglossary item: percentage  or anything other than frequencies
  • Expected values include small values. As a rule of thumb: If any expected value is zero or more than one fifth of the expected values are less than five, the chi-square test becomes unreliable. (Note that's expected values: it does not matter what the observed values are)