Pain scores on an ordinal scale are measured in the same group of patients before and after physiotherapy. The differences are not normally distributed. Which test is most appropriate to compare the paired observations?
- A Mann-Whitney U test
- B Wilcoxon signed-rank test ✓
- C Kruskal-Wallis test
- D Chi-square test
Correct answer: B. Wilcoxon signed-rank test
Explanation
The Wilcoxon signed-rank test is the non-parametric counterpart of the paired t-test and handles two related samples when the distribution of differences is not normal. Mann-Whitney U compares two independent groups and Kruskal-Wallis compares three or more independent groups, so both fail the paired design requirement. Recognising that pairing plus non-normality demands Wilcoxon rather than its independent-group analogue is the discriminating step.
Reference: Park's Textbook of Preventive and Social Medicine, 27th ed.
High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP
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