13.22. Analyze the Houses2 data file at the text website 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) Construct a scatterplot, identifying the points by whether the home is new or 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 this single observation. Again, test whether the interaction term is needed in the model.

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