Consider the simple linear regression model fit to the oxygen purity data in Problem 2.7.

Problem 2.7

The purity of oxygen produced by a fractional distillation process is thought to be related to the percentage of hydrocarbons in the main condensor of the processing unit. Twenty samples are shown below.

a. Construct a normal probability plot of the residuals. Does there seem to be any problem with the normality assumption?

b. Construct and interpret a plot of the residuals versus the predicted response.

Hydrocarbon Purity (%) (%) Purity (%) Hydrocarbon (%) 86.91 1.02 96.73 1.46 89.85 1.11 99.42 1.55 90.28 1.43 98.66 1.55 86.34 1.11 96.07 1.55 92.58 1.01 93.65 1.40 87.33 0.95 87.31 1.15 86.29 1.11 95.00 1.01 91.86 0.87 96.85 0.99 95.61 1.43 85.20 0.95 89.86 1.02 90.56 0.98