Statistical Analysis for Education and Psychology Researchers

Figure 8.1: Overlay plot of response

vs. explanatory and predicted vs.

explanatory variables

The normality assumption is checked by examining a normal probability plot of the
residuals from the fitted model. This is produced by the following SAS code:

proc univariate data=outreg plot;

var r; ** r represents the residuals from PROC REG

**;

run;

The SAS plot of the residuals is shown in Figure 8.2.

Inferences involving continuous data 271