A clinical trial comparing a new antihypertensive with placebo reports p = 0.04. Which of the following statements is CORRECT?
- A There is a 4% probability that the new drug has no effect
- B There is a 96% probability that the alternative hypothesis is true
- C If the null hypothesis were true, there is a 4% probability of observing results as extreme or more extreme by chance ✓
- D The study has 96% power to detect the true treatment effect
Correct answer: C. If the null hypothesis were true, there is a 4% probability of observing results as extreme or more extreme by chance
Explanation
The p-value is the probability of obtaining a test statistic as extreme as, or more extreme than, the observed value, assuming the null hypothesis is true. It does NOT represent the probability that the null hypothesis is true or that the alternative hypothesis is true. A p-value < 0.05 is conventionally significant, but it says nothing about the magnitude of effect (for that, we use effect size or confidence intervals) or study power (which is 1 − β, calculated separately).
Reference: Park's Textbook of Preventive and Social Medicine, 27th ed.
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