8 First order model, two predictors, and interaction y =  0 +  1 x 1 +  2 x 2 +  3 x 1 x 2 +  x1x1 X 2 = 2 X 2 = 3 X 2 =1  0 +  2 (1)] +[  1 +  3 (1)]x 1  0 +  2 (3)] +[  1 +  3 (3)]x1  0 +  2 (2)] +[  1 +  3 (2)]x 1 The two variables interact to affect the value of y.
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