Confounding and regression adjustment in difference-in-differences studies.

ABSTRACT:

Objective

To define confounding bias in difference-in-difference studies and compare regression- and matching-based estimators designed to correct bias due to observed confounders.

Data sources

We simulated data from linear models that incorporated different confounding relationships: time-invariant covariates with a time-varying effect on the outcome, time-varying covariates with a constant effect on the outcome, and time-varying covariates with a time-varying effect on the outcome. We considered a simple setting that is common in the applied literature: treatment is introduced at a single time point and there is no unobserved treatment effect heterogeneity.

Study design

We compared the bias and root mean squared error of treatment effect estimates from six model spe

SUBMITTER: Zeldow B 

PROVIDER: S-EPMC8522571 | biostudies-literature | 2021 Oct

REPOSITORIES: biostudies-literature