1. Propensity Scores: A Practical Method for Assessing Treatment Effects in Pain and Symptom Management Research 
Melissa M. Garrido, PhD 
Journal of Pain and Symptom Management 
Volume 48, Issue 4, Pages (October 2014)
DOI: /j.jpainsymman
Copyright © Terms and Conditions

2. Fig. 1
Propensity scores should include hypothesized strong confounders and weak confounders, but they should not include instrumental variables (Guidelines 1–3).
Journal of Pain and Symptom Management  , DOI: ( /j.jpainsymman )
Copyright © Terms and Conditions

3. Fig. 2
Covariates included in a propensity score should not be affected by the treatment variable. Variables that occur after the treatment variable are part of the causal pathway; including these in the propensity score will bias the treatment effect one is trying to estimate (Guideline 4).
Journal of Pain and Symptom Management  , DOI: ( /j.jpainsymman )
Copyright © Terms and Conditions