Relative effect (95% CI)

The relative effect will typically be a risk ratio or odds ratio (or occasionally a hazard ratio) with its accompanying 95% confidence interval, obtained from a meta-analysis performed on the basis of the same effect measure. Risk ratios and odds ratios are similar when the control intervention risks are low and effects are small, but differ considerably as these increase. The meta-analysis may involve an assumption of either fixed or random effects, depending on what the review authors consider appropriate.