solution

For the Well Elderly 2 data in Exercises 4 and 6, compare the regression lines using ancJN using the data labeled CESD (depressive symptoms) as the independent variable and LSIZ as the dependent variable. Use the data in the file A3 for the first group (the experimental group) and the file B1 as the second (control) group. Perform the analysis with leverage points removed.

Exercises 4

A portion of the data from the Well Elderly 2 study is stored in the author’s web page in the file A3 dat.txt. These are measures taken after intervention. Use the R function qhdsm to create a smooth for the 0.2, 0.5, and 0.8 quantiles using the data with the label MAPAGLOB as the independent variable (a measure of meaningful activities) and the data with the label LSIZ (life satisfaction) as the dependent variable. What does the smooth suggest about using the R function khomreg in Section 6.8.1 to test the hypothesis of homoscedasticity with leverage points removed?

Exercises 5

For the data in the previous exercise, test the hypothesis that the 0.8 quantile regression line has a zero slope with leverage points removed.

Exercises 6

Repeat Exercise 4, only use the data in the file B3 dat.txt. Comment on the results.

Exercises 4

A portion of the data from the Well Elderly 2 study is stored in the author’s web page in the file A3 dat.txt. These are measures taken after intervention. Use the R function qhdsm to create a smooth for the 0.2, 0.5, and 0.8 quantiles using the data with the label MAPAGLOB as the independent variable (a measure of meaningful activities) and the data with the label LSIZ (life satisfaction) as the dependent variable. What does the smooth suggest about using the R function khomreg in Section 6.8.1 to test the hypothesis of homoscedasticity with leverage points removed?