Sea bream are one type of fish that are often raised in large fish farming enterprises. These fish are usually fed a diet consisting primarily of fish meal. The authors of the paper “Growth and Economic Profit of Gilthead Sea Bream (Sparus aurata, L.) Fed Sunflower Meal”

(Aquaculture [2007]: 528–534) describe a study to investigate whether it would be more profitable to substitute plant protein in the form of sunflower meal for some of the fish meal in the sea bream’s diet. The accompanying data are consistent with summary quantities given in the paper for x 5 percentage of sunflower meal in the diet and y 5 average weight of fish after 248 days (in grams).
Sunflower Meal (%) Average Fish Weight 0 432 6 450 12 455 18 445 24 427 30 422 36 421 The estimated regression line for these data is y^ 5 448.536 2 0.696x and the standardized residuals are as given.
Sunflower Meal (%), x Standardized Residual 0 21.96 6 0.58 12 1.42 18 0.84 24 20.46 30 20.58 36 20.29 Construct a standardized residual plot. What does the plot suggest about the adequacy of the simple linear regression model?