The χ2 (chi-square) statistic is a measure of how well the observed data in a goodness of fit test fit the expected distribution. It quantifies the difference between observed and expected frequencies.
Related terms
Degrees of Freedom: This term refers to the number of categories or cells minus 1 in a goodness of fit test.
Observed Frequencies: These are the actual frequencies that we observe in our sample.
Expected Frequencies: These are the frequencies that we would expect to see in each category based on some theoretical distribution.