Statistics & Probability
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Chi-Square Statistic

Tests goodness of fit between observed and expected counts.

Formula

χ2=∑(O−E)2E\chi^2 = \sum \frac{(O-E)^2}{E}

Variables

OObserved
EExpected

Example

Larger = worse fit

Did You Know?

The chi-square test, devised by Karl Pearson in 1900, checks whether observed counts match what theory predicts.

hypothesis-test