Blood pressure was recorded in 50 hypertensive patients before starting amlodipine and again after 8 weeks of therapy on the same patients. The distribution of the differences is approximately normal. Which test is most appropriate to assess whether the drug changed blood pressure?
- A Paired t-test ✓
- B Independent samples t-test
- C Chi-square test
- D Mann-Whitney U test
Correct answer: A. Paired t-test
Explanation
When the same subjects are measured twice, such as before and after an intervention, the observations are paired, and the paired t-test compares the mean of within-subject differences. It requires the differences themselves to be roughly normally distributed, which is stated here. The independent t-test and Mann-Whitney U test are for two separate groups, and the chi-square test compares proportions, not continuous paired measurements.
Reference: Park's Textbook of Preventive and Social Medicine, 27th ed.
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