The StatCrunch printout below was obtained from fitting the model y = b0 + b1x1 + b2x2 + b3x1x2 + e to n = 15 data points.

a. What is the prediction equation?

b. Give an estimate of the slope of the line relating y to x1 when x2 = 10.

c. Plot the prediction equation for the case when x2 = 1. Do this twice more on the same graph for the cases when x2 = 3 and x2 = 5.

d. Explain what it means to say that x1 and x2 interact. Explain why your graph of part c suggests that x1 and x2 interact.

e. Specify the null and alternative hypotheses you would use to test whether x1 and x2 interact.

f. Conduct the hypothesis test of part e using a = .01. Applying the Concepts—Basic