What shape represents a confidence interval in meta-analysis?

In meta-analysis, a confidence interval is typically represented by horizontal lines. This visual representation illustrates the range of values within which the true effect size is likely to fall, based on the data from multiple studies. The horizontal line extends across the graph's domain, indicating the lower and upper limits of the confidence interval for the estimated effect.

The use of horizontal lines allows for easy comparison across different studies or interventions, showing how the effect sizes vary and where the overall effect size falls in relation to these confidence intervals. Understanding this representation is crucial for interpreting the reliability and precision of the estimated effects in a meta-analysis, as a wider confidence interval suggests greater uncertainty about the effect size.

The other shapes listed, such as diamonds, squares, and vertical lines, serve different purposes in a meta-analysis. Diamonds are often used to represent the summary effect size, while squares may indicate individual study effect sizes, and vertical lines are typically used to show the line of no effect. Thus, recognizing the specific role of horizontal lines in representing confidence intervals is essential for interpreting the results of a meta-analysis accurately.