Confidence Intervals

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95% CI = range that would contain the true value in 95% of repeated samples. Narrower = more precise (bigger n). Interpreting CIs for differences (no effect = 0) vs ratios (RR/OR no effect = 1): if the CI crosses the no-effect value → non-significant. CIs more informative than p-values (show magnitude + precision). ConfidenceIntervalDemo. Worked example reading an RR with CI. Highest-yield inferential concept.

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