Use the data in anthrop.dat for this problem.
a. Construct a population from the 3000 observations in anthrop.dat in which the 1000 individuals with the highest value of y have been removed. Now take an SRS of size 200 from the remaining 2000 individuals, and plot the data along with the ordinary least squares regression line. How does this line compare to the population regression line?
b. Repeat (a), but use as the population the 2000 individuals with the lowest value of x.
c. Is there a difference in the regression equations in (a) and (b)? Explain, and relate your findings to the model in (11.1).