5.38. Winning marathon times. Chance (Winter 2000) published a study of men's and women's winning times in the Boston Marathon. The researchers built a model for predicting winning time (y) of the marathon as a function of year (x1) in which the race is run and gender (x2) of the winning runner. Classify each variable in the model as quantitative or qualitative.
5.39. Snow goose feeding trial. Writing in the Journal of Applied Ecology (Vol. 32, 1995), botanists used multiple regression to model the weight change (y) of a baby snow goose subjected to a feeding trial. Three independent variables measured are listed below. Classify each as quantitative or qualitative.
(a) Diet type (plant or duck chow)
(b) Digestion ef?ciency (percentage)
(c) Amount of acid-?ber detergent added to diet (percentage)