ABSTRACT
D. The plot (see Exercise Figure 7.1) shows three well-separated classes, including a consistently low IS class, a moderate and increasing IS class, and a chronically high IS class.
E. The mean quality test (see Exercise Table 7.3) also provided evidence that the model has a clear classification. The intercept means were statistically different across the three classes. Also, the slope mean for the moderate and increasing class was significantly higher than the slope means for the consistently low and chronically high IS classes.
