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 βthe sum of squared deviations of each observed effect from
the mean effect on a standardized scaleβ (Borenstein, 2019, p. 457).
The Q-statistic can be calculated using the following formula:
(πΈππ’ππ‘πππ 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):
(πΈππ’ππ‘πππ 8)