can a random effect bias be induced by a covariate do unmeasured covariates induce bias do unmeasured covariates induce bias? how does a random effect in a group model impact the parameters of each covariate does a random effect change the parameter estimate for a group level covariate? random effects definition do unmeasured covariates induce bias how does the random effect of a random effect of the patient affect the model what is the difference between a fixed and unmeasured effect? how do random effect models work can you have a fixed effect model random bias definition what if i added random effect to my model when to use random random effect do hospital based random effects models induce bias why can't you do a fixed effects model can random effects be used for a fixed effects model do random effects alter parameters why do you add random random effect to a model of delay to treatment? how to model delay to treatment