I² statistic

The I² statistic measures how much variability or difference exists between the results of multiple studies in a meta-analysis, beyond what we would expect by chance. It indicates the percentage of total variation that is due to real differences rather than random error. An I² close to 0% suggests studies are very consistent, while higher values (like 50% or more) imply substantial differences, possibly due to variations in study populations, methods, or other factors. It helps researchers understand whether the combined results are reliable or if underlying differences need further exploration.