Confidence Interval — What It Means in Clinical Trials
Plain English Definition
A confidence interval (CI) is a range of values that likely contains the true effect of a treatment. A 95% confidence interval means researchers are 95% confident the true result falls within that range. A narrow confidence interval means the estimate is precise. A wide one means there is more uncertainty.
Why It Matters
Confidence intervals give you a sense of how precise the trial results are. If a trial reports median survival of 15 months (95% CI: 12-18), the true benefit is likely somewhere between 12 and 18 months.
Example
A trial might report: "Hazard ratio: 0.65 (95% CI: 0.52-0.81)." Since the entire range is below 1.0, the treatment consistently shows a benefit.
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