Which single modification will increase the statistical power of a planned trial comparing two antihypertensive drugs, all else being equal?
- A Decreasing the sample size
- B Increasing the sample size ✓
- C Raising the level of significance above 0.05
- D Increasing the expected difference between treatments
Correct answer: B. Increasing the sample size
Explanation
Power is 1 minus beta, the probability of detecting a true difference when it exists, and it rises as sample size increases because standard error falls. Raising alpha also raises power but at the cost of more false positives, so option C changes the error balance rather than improving the study. Option D is not under investigator control in a fixed comparison, and option A reduces power, making B the only defensible design modification.
Reference: Park's Textbook of Preventive and Social Medicine, 27th ed.
High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP
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