Analysis of a Detroit Marathon (n = 1,015 men, n = 150 women) produced the regression results shown below, with dependent variable Time (the marathon time in minutes) and predictors Age (runner's age), Weight (runner's weight in pounds), Height (runner's height in inches), and Exp (1 if runner had prior marathon experience, 0 otherwise).
(a) Interpret the coefficient of Exp.
(b) Does the intercept have any meaning?
(c) Why do you suppose squared predictors were included?
(d) Plug in your own Age, Height, Weight, and Exp to predict your own running time. Do you believe it? (Data courtesy of Detroit Striders.)

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Men (n = 1,015) Women (n = 150) Variable Coefficient 2 6 0.05240 N Height aleem 24.65 一17.0 = 0.423 R2 = 0.334