Heterogeneity Analysis

There are several methods for estimating heterogeneity in meta-analyses including Q, I2, andT2 statistics. In the current study, bothQ and I2 statistics were computed. TheQ-statistic follows a chi-squared distribution with degrees of freedom equal to the number of effect sizes/studies minus 1, and it is defined as β€œthe sum of squared deviations of each observed effect from the mean effect on a standardized scale” (Borenstein, 2019, p. 457). The Q-statistic can be calculated using the following formula:
(πΈπ‘žπ‘’π‘Žπ‘‘π‘–π‘œπ‘› 7)
Where Wi is the study weight, Yi is the study effect size,M as the summary effect, and k is the number of effect sizes.I2-statistic refers to the proportion of the observed variance, which can be estimated using the following formula (Borenstein et al., 2021):
(πΈπ‘žπ‘’π‘Žπ‘‘π‘–π‘œπ‘› 8)