Fig. 4

Results of the simulation study showing mean squared error (MSE) of estimates with weak modification (strength of modification = 0.0) up to strong modification (strength of modification = 0.5). Top panel: Scenario A (all effect modifiers are non-colliders); middle panel: Scenario B (some effect modifiers are colliders); bottom panel: Scenario C (effect modifiers are colliders and influence the causal effect in a complex way). The black line represents results with no stratification. In each scenario, data are independently simulated 100 times, and the MSE represents the median value across simulations