Consider the regression model fit to the X-ray inspection data in Exercise 12-15. Use rads as the response.

(a) What proportion of total variability is explained by this model?

(b) Construct a normal probability plot of the residuals. What conclusion can you draw from this plot?

(c) Plot the residuals versus y and versus each regressor, and comment on model adequacy.

(d) Calculate Cook€™s distance for the observations in this data set. Are there any influential points in these data?

Transcribed Image Text:

mAmps Exposure Time Rads 7.4 10 0.25 14.8 10 0.5 29.6 10 59.2 10 88.8 10 3 296 10 10 444 10 15 592 10 20 15 0.25 11.1 22.2 15 0.5 44.4 15 88.8 15 2 133.2 15 3 444 15 10 666 15 15 888 15 20 14.8 20 0.25 29.6 20 0.5 59.2 20 118.4 20 2 177.6 20 3 592 20 10 888 20 15 1184 20 20 22. 30 0.25 44.4 30 0.5 88.8 30 177.6 30 2 266.4 30 888 30 10 1332 30 15 1776 30 20 29.6 40 0.25 59.2 40 0.5 118.4 40 236.8 40 2 355.2 40 3 1184 40 10 1776 40 15 2368 40 20