2 . Fit a quadratic model 3 - Bot . Big + B 2 2 2 + 3 2 1 2 2 + Baz + Buzz + Remember that to get the quadratic terms , you need to use , for example , I ( age 1 2 ) in the model specification Plot the residuals from the quadratic model versus age and water temperature , and make a normal QQ plot of the residuals using the ggnorm command . Comment on whether the quadratic model seems appropriate