A hospital evaluates a hand hygiene programme among its own staff by measuring compliance before and after training in the same 200 nurses, recording each nurse as compliant or non-compliant on both occasions. Which statistical test is appropriate to assess whether the proportion compliant changed significantly?
- A Standard Pearson chi-square test
- B Fisher exact test
- C McNemar test ✓
- D Z-test for two independent proportions
Correct answer: C. McNemar test
Explanation
McNemar test is designed for paired nominal data, where the same subjects are classified twice into binary categories. It focuses on the discordant pairs, nurses who changed status in either direction, and ignores concordant pairs who stayed compliant or non-compliant. A conventional chi-square or z-test treats the two time points as independent groups, which is false here and inflates the apparent sample size, violating the independence assumption underlying both.
Reference: Park's Textbook of Preventive and Social Medicine, 27th ed.
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