To do this, we measure the average causal effect of an intervention by first estimating its effect at each “level,” or stratum, of the deconfounder. We then compute a weighted average of those strata, where each stratum is weighted according to its prevalence in the population. If, for example, the deconfounder is gender, we first estimate the causal effect for males and females. Then we average the two, if the population is (as usual) half male and half female. If the proportions are different—say, two-thirds male and one-third female—then to estimate the average causal effect we would take a
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