Thanks to Tim Morris for letting me know about a paper just published in the journal Clinical Trials by Zhang et al, titled ‘Conditional estimation and inference to address observed covariate imbalance in randomized clinical trials’. Zhang et al propose so called conditional estimation and inference to address observed covariate imbalance in randomised trials. They introduce the setup of randomised trials with covariates 
, randomised treatment 
, and outcome 
. They begin with a framework that treats all three as random in repeated sampling, and review the unadjusted estimator of the marginal mean difference in outcome, and a covariate adjusted estimator based on earlier work by Tsiatis and others.