Dear Stata Experts:
I have two questions regarding regression analysis:

1. What is the difference between a nested regression and hierarchical linear modeling? I ran both and got the same results
The dependent variable is a continuous and normally distributed math score; the primary predictor is maternal education represented by 5 categories: less than high school, high school, some college, college and graduate school. In addition there are several other students and family traits added in steps

2. After running a nested regression, I analyzed the residuals and the graphed results are shown below. Can I justify use of the OLS model despite the fact that the model is underestimating results for lower end students? Is there an alternative way to analyze the effect of maternal ed on math outcomes? I appreciate your help!



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