The file FTMBA contains a sample of top-ranked full-time MBA programs. Variables included are mean starting salary upon graduation ($), percentage of students with job offers within three months of graduation, program cost ($), and total number of students per program.

a. Using all the data as the training sample, develop a regression tree model to predict the mean starting salary upon graduation.

b. What conclusions can you reach about the mean starting salary upon graduation?

c. Using half the data as the training sample and the other half of the data as the validation sample, develop a regression tree model to predict the mean starting salary upon graduation.

d. What differences exist in the results of (a) and (c)?