A researcher conducts a study and reports a p-value of 0.03. The pre-specified alpha was 0.05. Which of the following interpretations is CORRECT?
- A There is a 3% probability that the null hypothesis is true
- B If the null hypothesis is true, there is a 3% probability of obtaining results as extreme as observed ✓
- C The alternative hypothesis has 97% probability of being true
- D The study has 97% statistical power
Correct answer: B. If the null hypothesis is true, there is a 3% probability of obtaining results as extreme as observed
Explanation
The p-value is the probability of observing a test statistic as extreme as (or more extreme than) the one obtained, assuming the null hypothesis is true. It is NOT the probability that the null hypothesis is true (that would require Bayesian reasoning with a prior). A p-value of 0.03 < alpha 0.05 means the result is statistically significant, allowing rejection of the null hypothesis, but does not quantify the probability of either hypothesis. Statistical power is 1 − beta, a separate concept.
Reference: Park's Textbook of Preventive and Social Medicine, 27th ed.
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