In addition, the PLINK meta-analysis output provides a measure of heterogeneity with a P-value for Cochrane’s Q statistic. This heterogeneity index in a meta-analysis refers to the variation in outcomes (betas) between studies. The Q statistic is calculated as the weighted sum of the squared differences between individual study effects (individual betas) and pooled effects (summary beta) across studies. Q has a chi-squared distribution with number of studies minus one degree of freedom.
