her-level residuals and a useful first step in diagnosing a model; however, for small group sample sizes, LS residuals are unreliable. Level-1 EB residuals are defined as the conditional modes of the random effects given the data and the estimated parameter values, which are calculated with (restricted) maximum likelihood. They are confounded with higher-level residuals, but more robust with small sample sizes. For higher-level residuals, coefficients can again be estimated using either LS or EB, but EB res