A study reports a p-value of 0.04. The researchers conclude that the intervention is effective. Which limitation of this interpretation is MOST important to recognise?
- A P-value < 0.05 definitively proves the alternative hypothesis is true
- B The p-value is the probability that the null hypothesis is true
- C A significant p-value does not convey the magnitude or clinical importance of the effect ✓
- D P-values can only be used with parametric data
Correct answer: C. A significant p-value does not convey the magnitude or clinical importance of the effect
Explanation
A p-value indicates the probability of observing results at least as extreme as those obtained, assuming the null hypothesis is true; it does not measure effect size or clinical relevance. With large sample sizes, trivially small differences can be statistically significant. Effect size measures (Cohen's d, OR, RR) and confidence intervals are needed to judge clinical importance.
Reference: Park's Textbook of Preventive and Social Medicine, 27th ed.
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