Title: 12.4.1 Confidence intervals
Headings: 12.4.1
Confidence intervals

12.4.1 Confidence intervals
Content: 12.4.1 Confidence intervals
Show
Home > Part 2: General methods for Cochrane reviews > 12 Interpreting results and drawing conclusions > 12.4 Interpreting results of statistical analyses > 12.4.1 Confidence intervals
12.4.1 Confidence intervals
Results for both individual studies and meta-analyses are reported with a point estimate together with an associated confidence interval. For example, “The odds ratio was 0.75 with a 95% confidence interval of 0.70 to 0.80”. The point estimate (0.75) is the best guess of the magnitude and direction of the experimental intervention’s effect compared with the control intervention. The confidence interval describes the uncertainty inherent in this estimate, and describes a range of values within which we can be reasonably sure that the true effect actually lies. If the confidence interval is relatively narrow (e.g. 0.70 to 0.80), the effect size is known precisely. If the interval is wider (e.g. 0.60 to 0.93) the uncertainty is greater, although there may still be enough precision to make decisions about the utility of the intervention. Intervals that are very wide (e.g. 0.50 to 1.10) indicate that we have little knowledge about the effect, and that further information is needed. A 95% confidence interval is often interpreted as indicating a range within which we can be 95% certain that the true effect lies. This statement is a loose interpretation, but is useful as a rough guide.