A family counselor believes that there is a relationship between number of years married and blood pressure. For each married man in a random sample, the number of years married (x) and the systolic...

A family counselor believes that there is a relationship between number of years married and blood pressure. For each married man in a random sample, the number of years married (x) and the systolic blood pressure ( y, in mmHg) were recorded. The data are given in the following table.

The estimated regression line is y = 97.95 1 4.034x.

a. Compute the residuals, and verify that they sum to 0.

b. Carefully sketch a normal probability plot for the residuals. Is there any evidence that the random error terms are not normal? Justify your answer.