In a case-control study of 30 participants examining the association between smoking and oral cancer, a 2x2 contingency table is constructed. One cell has an expected frequency of 3. Which statistical test is most appropriate?

• A Chi-square test without correction
• B Chi-square test with Yates correction
• C McNemar's test
• D Fisher's exact test ✓

Explanation

When any expected cell frequency in a 2x2 table is below 5, Fisher's exact test is preferred because the chi-square approximation becomes unreliable. Yates correction is sometimes used for small samples but Fisher's exact test is the gold standard when expected frequencies are very low. McNemar's test is for paired or matched data.

Reference: Methods in Biostatistics, 7th ed.

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