The article “Validation of the Rockport Fitness Walking Test in College Males and Females” (Research Quarterly for Exercise and Sport, 1994: 152–158) recommended the following estimated regression equation for relating (L/min, a measure of cardiorespiratory fitness) to the predictors

, and heart rate at the end of the walk (beats/min):

a. How would you interpret the estimated coefficient

?

b. How would you interpret the estimated coefficient

?

c. Suppose that an observation made on a male whose weight was 170 lb, walk time was 11 min, and heart rate was 140 beats/min resulted in . What would you have predicted for VO2max in this situation, and what is the value of the corresponding residual?

d. Using and , what proportion of observed variation in VO2max can be attributed to the model relationship?

e. Assuming a sample size of , carry out a test of hypotheses to decide whether the chosen model specifies a useful relationship between VO2max and at least one of the predictors.