Propensity score matching is a statistical technique used in observational studies to reduce bias and ensure comparability between treatment and control groups. It involves creating a propensity score, which estimates the likelihood of an individual receiving a particular treatment based on their observed characteristics. This score is then used to match individuals in the treatment group with similar individuals in the control group, allowing for a more unbiased comparison of outcomes between the two groups. Propensity score matching is often used in healthcare and social science research to evaluate the effectiveness of interventions or policies when randomized controlled trials are not feasible or ethical.