13.22. Analyze the "house selling price 2" data file at the text Web site by modeling selling price in terms of size of house and whether it is new.

(a) Fit the model allowing interaction, and test whether the interaction term is needed in the model.

(b) Figure 13.14 shows a scatterplot, labeling the points by a 1 when the home is new and a 0 when it is not. The observation with the highest selling price is a new home that is somewhat removed from the general trend of points. Fit the interaction model after removing thissingle observation. Again, test whether the interaction term is needed in the model.

Note what a large impact one observation can have on the conclusions.