Confidence Interval
A range of values within which the true treatment effect is likely to fall, typically calculated at the 95% level. A 95% confidence interval means that if the trial were repeated 100 times, approximately 95 of those intervals would contain the true effect. Narrower intervals indicate more precise estimates.
Technical Context
A 95% CI means: if we repeated this experiment many times, approximately 95% of the calculated intervals would contain the true population parameter. The width of the CI reflects precision — narrower intervals indicate more precise estimates (larger sample sizes produce narrower CIs). For clinical decision-making, CI lower and upper bounds are more informative than p-values alone. If a 95% CI for weight loss difference excludes zero, the result is statistically significant at p<0.05. The clinical interpretation considers whether the entire CI represents clinically meaningful values. For non-inferiority trials, the CI must lie entirely above the pre-specified non-inferiority margin.