Homework 3:

1. Fit a regression line of height on age. Calculate the correlation
coefficient between theses two variables. Interpret you results.

2. Create a new variable PLUC.ch to indicate the change from baseline
PLUC (PLUC.pre - PLUC.post) using the dataset 1 in our course website.
Consider this new variable as your response variable. Perform
two-factor ANOVA of this new variable using treatment groups and
shades as factors.