The above weighted regression model, where the residual standard error is set to one, is equivalent to performing a fixed‐effect meta‐analysis of the variant‐specific causal estimates.18 Under a multiplicative random effects model, the residual standard error can be greater than one, allowing for heterogeneity in the causal estimates. The point estimate from the fixed and random effect models will be the same, but the standard error of the causal effect from the multiplicative random effects model will be larger if there is heterogeneity between the causal estimates. Throughout this paper, we apply a multiplicative random effects model to all the analyses.
