A confidence interval for a risk ratio is reported as 1.4 (95% CI: 1.1–1.8) with a p-value of 0.003. Which of the following conclusions is MOST appropriate?
- A The association is statistically significant and likely not due to chance alone ✓
- B There is a 95% probability that the true risk ratio is exactly 1.4
- C The p-value of 0.003 proves that the exposure causes the outcome
- D The confidence interval indicates that 95% of individuals have a risk ratio between 1.1 and 1.8
Correct answer: A. The association is statistically significant and likely not due to chance alone
Explanation
A 95% CI that excludes 1.0 for a risk ratio and a p-value < 0.05 indicate statistical significance, meaning the result is unlikely due to chance alone. However, statistical significance does not establish causality — confounding, bias, and chance must all be considered. The 95% CI means that if the study were repeated 100 times, 95 of the resulting CIs would contain the true population value — it is not a probability statement about the specific observed interval nor a distribution across individuals.
Reference: Park's Textbook of Preventive and Social Medicine, 27th ed.
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