Inverse propensity weighting estimates an average treatment effect by reweighting each observation according to the inverse probability of receiving its observed treatment. It turns propensity scores into a way to calculate causal effects rather than merely describe treatment assignment. section 5.3.4
The method connects propensity scores to the adjustment formula: patients with their treatment probabilities represented by scores can support an unbiased causal-effect estimate when relevant confounders are not missing. section 5.3.4
Use it with these conditions and distinctions:
- Check the positivity assumption before using the calculated scores. section 5.3.4
- Treat the method as an alternative relationship between propensity scores and the adjustment formula, alongside other numerical implementations. section 5.3.4
- Recognize that unbiasedness still depends on not omitting relevant confounders. section 5.3.4
Table 5.2 Available data with propensity scores calculated
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Inspect patient-level treatment, outcome, confounder, and propensity-score data before applying the weighting approach. section 5.3.4
