Home-work 4:  Stat 350:

    1. Use the data set you used in HW 3 and answer the following questions.
 
    a. Do two iterations of weighted least squares.
    b. Run robust regression (M with Huber weights) to see if influential observations were an issue
    c. Use Ridge Regression to see with c between .01 and .1 and provide the ridge plot
    2. Do plots of residual versus predicted and residual versus observed?  Are they the same plot?  Comment on your findings.
    3. Instead of doing residual analysis with residuals (for the example above) use the observed Y’s.  Look at plots and tests.  What do you get?