题目要求是分别生成两个Multilevel regression model，然后用graphically and numerically的方法比较两个模型。可能我的英语理解有问题，除了比较fix effect, random effect和AIC数值外，想不出有什么图表可以比较的，求指导应该如何比较？

原题如下:
(a) Write a model predicting CD4 percentage as a function of time with varying
intercepts across children. Fit using lmer() and interpret the coefficient for
time.
(b) Extend the model in (a) to include child-level predictors (that is, group-level
predictors) for treatment and age at baseline. Fit using lmer() and interpret
the coefficients on time, treatment, and age at baseline.
(c) Investigate the change in partial pooling from (a) to (b) both graphically and
numerically.