Data for 100 college students were used to estimate this multiple regression equation:

Y = −0.752 + 0.470F + 0.507M + 0.047A + 4.330D, where Y = height of student

(inches), F = height of student’s biological father (inches), M = height of student’s biological mother (inches), A = student’s age (years), and D = 1 if the student is male and 0 if female.

a. What is the predicted effect on a student’s height if the heights of the father and mother are both increased by 1 inch?

b. Explain why you either agree or disagree with this interpretation of the results:
“Men were, on average, 4.33 inches taller than women.”

c. Are the results invalidated by the fact that this equation predicts a negative height if all of the explanatory variables equal 0?