In the article "Bigger Teeth for Longer Life? Longevity and Molar Height in Two Roe Deer Populations" (Biology Letters [June, 2007] vol. 3 no. 3 268-270), researchers developed a model to predict the tooth height (in mm), y, of roe deer based on their age, x1, gender, x2 (0 = female, 1 = male), and location, x3 (Trois Fontaines deer, which have a shorter life expectancy, and Chizé, which have a longer life expectancy, x3 = 0 for Trois Fontaines, x3 = 1 for Chizé). The model is
y̅ = 7.790 - 0.382x1 - 0.587x2 - 0.925x3 + 0.091x2x3
(a) What is the expected tooth length of a female roe deer who is 12 years old and lives in Trois Fontaines?
(b) What is the expected tooth length of a male roe deer who is 8 years old and lives in Chizé?
(c) What is the interaction term? What does the coefficient of the interaction term imply about tooth length?