A researcher calculates an Odds Ratio of 3.5 with a 95% confidence interval of 1.2 to 10.4 for the association between smoking and disease X. Which statement is MOST appropriate?
- A The association is not statistically significant because the confidence interval is wide
- B The association is statistically significant at p < 0.05 ✓
- C The OR of 3.5 means smoking causes disease X with 3.5 times certainty
- D The study must have been a randomised controlled trial
Correct answer: B. The association is statistically significant at p < 0.05
Explanation
A 95% confidence interval that does not cross 1.0 indicates statistical significance at p < 0.05; here 1.2 to 10.4 does not include 1.0, so the association is significant. Width of the CI reflects precision but does not determine significance. OR is a measure of association, not causation, and is typically used in case-control studies, not RCTs.
Reference: Park's Textbook of Preventive and Social Medicine, 27th ed.
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