A researcher conducts a matched pair case-control study of oral cancer and tobacco use, analysing discordant pairs between cases and their matched controls. The appropriate statistical test is:

• A Standard chi-square test
• B Mann-Whitney U test
• C Fisher's exact test
• D McNemar's test ✓

Explanation

McNemar's test is designed for paired nominal data, comparing proportions within matched pairs or within the same subject tested twice. It uses only the discordant pairs, those where case and control differ in exposure status. Applying an ordinary chi-square would ignore the pairing and inflate significance falsely. Fisher exact test suits unpaired small tables, and Mann-Whitney U compares ordinal data between independent groups.

Reference: Park's Textbook of Preventive and Social Medicine, 27th ed.

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