. Suppose the research department for Century Tire Company is developing a snow tire based on a new formulation. A study was conducted to examine the relationship between the amount of the new...

. Suppose the research department for Century Tire Company is developing a snow tire based on a new formulation. A study was conducted to examine the relationship between the amount of the new additive per liter (x, in mL) and the amount of wear after 50,000 indoor test miles (y, in mm). A simple linear regression analysis was conducted, and the following residuals were obtained.

a. Carefully sketch a normal probability plot for the residuals.

b. Is there any evidence that the random error terms are not normal? Justify your answer.