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Propensity Scores

  • Gideon J. MellenberghEmail author
Chapter

Abstract

A quasi-experiment is a study, where the researcher manipulates the IV, but participants are not randomly assigned to conditions. Therefore, it is prone to selection bias. The propensity score method reduces the systematic error of selection bias if some conditions are fulfilled. A participant’s propensity score is his or her probability of belonging to the E-condition. The propensity score method consists of two phases. First, the propensity scores are estimated from sample data. A set of auxiliary variables of the participants is measured. These variables are used to estimate participants’ propensity scores. For example, if the IV has two (E- and C-) conditions, the auxiliary variables and logistic regression are applied to estimate a participant’s probability of belonging to the E-condition. Second, effects of the IV on the DV are estimated using the propensity scores to reduce selection bias. For example, groups of participants are matched on their propensity scores, and condition effects are estimated per matched group. The propensity score method corrects for selection bias of the auxiliary variables, but not for bias of variables that are not measured.

Keywords

Hidden and overt selection bias Logistic regression model Quasi-experimental study Subclassification propensity score method 

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Copyright information

© Springer Nature Switzerland AG 2019

Authors and Affiliations

  1. 1.Emeritus Professor Psychological Methods, Department of PsychologyUniversity of AmsterdamAmsterdamThe Netherlands

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