Cardiorespiratory fitness is widely recognized as a major component of overall physical well-being. Direct measurement of maximal oxygen uptake (VO2max) is the single best measure of such fitness, but direct measurement is time-consuming and expensive. It is therefore desirable to have a prediction equation for VO2max in terms of easily obtained quantities. Consider the following variables.

y = VO2max (L/min)
x1 = weight (kg)
x2 = age (yr)
x3 = time necessary to walk 1 mile (min)
x4 = heart rate at the end of the walk (beats/min)

Here is one possible model for male students, consistent with the information given in the article "Validation of the Rockport Fitness Walking Test in College Males and Females."†

Y = 5.0 + 0.01x1 − 0.05x2 − 0.13x3 − 0.01x4 + ϵ

σ = 0.4

(a) Interpret β1.

(b) What is the expected value of VO2max when weight is 76 kg, age is 25 yr, walk time is 14 min, and heart rate is 138 b/m?
L/min

(c) What is the probability that VO2max will be between 0.59 and 2.03 for a single observation made when the values of the predictors are as stated in part (b)? (Round your answer to four decimal places.)