In a cohort study examining the association between pesticide exposure and Parkinson's disease, the risk ratio is 2.4 and the 95% confidence interval is (0.9, 6.3). Which statement best describes this result?

• A The result is not statistically significant at alpha 0.05 because the CI includes 1.0 ✓
• B The association is statistically significant since the point estimate exceeds 1.0
• C The wide CI indicates systematic bias and the study should be discarded
• D A p-value < 0.05 is guaranteed since the lower bound is close to 1.0

Explanation

A 95% confidence interval that spans 1.0 (the null value for a ratio measure) means the result is not statistically significant at alpha = 0.05. The point estimate of 2.4 suggests a potentially important effect, but the wide CI reflects imprecision, likely due to small sample size or few events. Statistical significance and clinical/epidemiological significance are distinct; non-significance does not equate to absence of association, but rather insufficient evidence. The CI width reflects random error (imprecision), not systematic bias.

Reference: Park's Textbook of Preventive and Social Medicine, 27th ed.

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