A well-conducted trial concludes there is no difference between two antihypertensives, but in reality drug A is superior. The error made, and its complement, are:
- A Type I error; power = 1 minus alpha
- B Type II error; power = 1 minus beta ✓
- C Type I error; power = 1 minus beta
- D Type II error; power = 1 minus alpha
Correct answer: B. Type II error; power = 1 minus beta
Explanation
Failing to reject a null hypothesis that is actually false is a Type II (beta) error, a false-negative result. Power is the probability of detecting a real difference when it exists, defined as 1 minus beta, conventionally set at 80% or 90% during sample size calculation. Type I error (alpha) is the opposite mistake: declaring a difference when none exists, so options involving alpha describe the wrong error direction.
Reference: Park's Textbook of Preventive and Social Medicine, 27th ed.
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