摘要：Evaluations of programmes — for example, labour market interventions such as employ-ment schemes and training courses — usually involve comparison of the performance of a treatmentgroup (recipients of the programme) with a control group (non-recipients) as regards some response(gaining employment, for example). But the ideal of randomisation of individuals to groups is rarelypossible in the social sciences and there may be substantial differences between groups in thedistributions of individual characteristics that can affect response. Past practice in economics hasbeen to try to use multiple regression models to adjust away the differences in observed charac-teristics, while also testing for sample selection bias. The Propensity Score approach, which iswidely applied in epidemiology and related fields, focuses on the idea that "matching" individualsin the groups should be compared. The appropriate matching measure is usually taken to be theprior probability of programme participation. This paper describes the key ideas of the PropensityScore method and illustrates its application by reanalysis of some Irish data on training courses
