Consider the first order model equation in 3 quantitives independent variables:
E (y)= 1_ 2x_1 +x_2 -3x_3
a) graph the relationship between y and x_1 or x_2=1 and x_3=3
b) repeat part a for x_2= -1 and x_3=1
c) How do you the graphed lines in parts a and b related to each other? What is the slope of each line?
d) If a linear model is first order in three independent variables, what type of geometric relationship will you obtain when E(y) is graphed as a function of one of the independent variables for various combinations of values of the other independent variables?