χ2
Definition
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.
Analogy
Think of the χ2 statistic as a measuring tape that tells us how closely our observed data matches what we would expect. Just like a measuring tape helps us determine if something fits properly, the χ2 statistic helps us determine if our data fits the expected distribution.
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.
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