Fifty hypertensive patients have their systolic blood pressure recorded before starting a salt-reduction programme and again after 12 weeks on the programme. The differences in readings are approximately normally distributed. The most appropriate test to determine whether the programme changed blood pressure is:

• A Paired t-test ✓
• B Unpaired (independent samples) t-test
• C Chi-square test
• D One-way ANOVA

Explanation

The same subjects are measured twice, producing paired observations, and the differences are normally distributed, so the paired t-test is correct. An unpaired t-test applies to two independent groups, which is not the design here. Chi-square compares proportions, not continuous means. One-way ANOVA compares means across three or more independent groups. Recognising paired versus unpaired designs is a frequently examined distinction.

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

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