Propensity Score Methods for Confounding Control in Nonexperimental Research

Nonexperimental studies are increasingly used to investigate
the safety and effectiveness of medical products as they are
used in routine care. One of the primary challenges of such
studies is confounding, systematic differences in prognosis
between patients exposed to an intervention of interest and
the selected comparator group. In the presence of uncontrolled
confounding, any observed difference in outcome risk
between the groups cannot be attributed solely to a causal
effect of the exposure on the outcome.