In a meta-analysis, what does a diamond shape signify?

In a meta-analysis, the diamond shape symbolizes the overall effect size derived from the combination of the effect sizes of multiple studies included in the analysis. The width of the diamond represents the confidence interval for this overall effect estimate. This visualization allows researchers and readers to quickly understand the pooled results of different studies, how closely the studies' results align, and the degree of uncertainty surrounding the calculated effect size.

The diamond's position indicates the central tendency of the data, and if it crosses the line of no effect (often represented as a vertical line at zero), it suggests that the overall effect may not be statistically significant. When the diamond is entirely to one side of this line, it indicates a statistically significant effect in that direction. Thus, the correct interpretation is that the diamond effectively conveys the main effect of the studies combined, making it an essential visual element in meta-analysis reporting.