- model 1: 0.41
 - model 2: 0.94
 - model 3: 0.71

- model 1: within-group variance (residual) = 0.0020; between-group variance (intercept) = 109.49 and random-slope variance = 122.01
- model 2: within-group variance (residual) = 16795.18; between-group variance (intercept) = 194633.337 and random-slope variance =1201.528
- model 3: within-group variance (residual) = 700.46; between-group variance (intercept) = 270.69 and random-slope variance = 0.02