Confidence Interval

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Definition

A confidence interval is a range of values that likely contains the true effect size, based on the data and statistical assumptions of a study.

Correct Scientific Usage

Confidence intervals provide information about both the estimated effect and the precision of that estimate. Wider intervals indicate greater uncertainty; narrower intervals suggest more precise estimates. Scientists recognize that confidence intervals provide more information than p-values alone.

Common Misunderstandings

The most common misunderstanding is interpreting a 95% confidence interval as meaning there is a 95% probability that the true value is in this range. The correct interpretation is that if we repeated the study many times, 95% of calculated intervals would contain the true value.

Some people may not consider whether the entire confidence interval represents clinically meaningful effects.

Why It Matters

Confidence intervals offer more interpretive value than p-values alone, helping readers assess uncertainty, plausibility, and real-world relevance rather than focusing on arbitrary thresholds.

References

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