is it justified to use a linear model when there isn't any variability why use a linear model and random effect what model should be used for random effects if there is no variability can there be no variability in an empty model? why should random effects be applied if there is no variability within a linear model, can a random effect be triggered without a linear model what level does an empty logistic model have no variable what level of variability is an empty model hlm is justified when the data is empty is random effects justified if there is no variability between groups? why a linear model is used in an empty model? why use an empty model random effects justified when there no variability what level of variability can hlm apply if there is no variability between groups in a linear model should hlm be applied just because data is theoretically nested? what level of variability are random effects justified when there is no variability between the data when random effects exist, how do they occur what if a random effect is justified when there is no variability, do random effects have to be applied a linear model what is random effects