Use the dataset cholesterol on the companion website. For n = 28 heart attack patients, the variables 2-Day and 4-Day are cholesterol levels measured 2 days and 4 days, respectively, after the attacks.
a. Plot 4-Day (y) versus 2-Day (x). Describe the direction and strength of the relationship, and comment on whether there are any outliers.
b. Determine the equation of the regression line relating y = 4-Day to x = 2-Day. Write the equation.
c. What is the value of the slope of the equation? Write a sentence that interprets the slope in the context of these variables.
d. Separately estimate cholesterol levels four days after the attack for patients with 2-Day values of 200, 250, and 300.
e. Utilizing the results of part (d), describe how cholesterol levels are predicted to change in the time from 2 days to 4 days after their heart attacks.