Research Measurements
CI
Confidence Interval
A range of values likely to contain the true effect size, typically at 95% confidence.
A confidence interval (CI) provides a range within which the true population parameter is likely to fall, with a specified level of confidence (typically 95%). A 95% CI means that if the study were repeated many times, 95% of the calculated intervals would contain the true value. Narrow confidence intervals indicate precise estimates, while wide intervals suggest uncertainty. In supplement research, if a 95% CI for a treatment effect includes zero (or 1.0 for ratios), the result is not statistically significant at the 0.05 level.