Chi-square test of independence — what does it do?

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Answer

$Tests whether two categorical variables are independent, given an r \times c contingency table.$
${\chi}^{2}\; = \;{\Sigma}$
$E_{\mathrm{ij}}$
$Use case: is conversion rate independent of region?$
$For small counts, use Fisher's exact test instead.$

Check yourself — multiple choice

For continuous data
${\chi}^{2}\; = \;{\Sigma}$ $(O - E)^{2} / E$ on contingency table; independence null; df=(r-1)(c-1); needs E ≥ 5 or use Fisher exact
Only 2×2 tables
Same as t-test

Chi-square independence: contingency table, E ≥ 5, else Fisher exact.

#hypothesis-testing#parametric-tests

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