For Exercises 11.59 to 11.61, see page 568; for 11.62 and 11.63, see page 571; for 11.64 to 11.66, see pages 474–575; for 11.67 and 11.68, see page 577; for 11.69 to 11.72, see page 580.

Question 11.72

11.72 Residuals.

CASE 11.3 Once we have chosen a model, we must examine the residuals for violations of the conditions of the multiple regression model. Examine the residuals from the model in Example 11.26.

  1. Plot the residuals against SqFt. Do the residuals show a random scatter, or is there some systematic pattern?
  2. The residual plot shows three somewhat low residuals, between −$20,000 and −$40,000. Which homes are these? Is there anything unusual about these homes?
  3. Make a Normal quantile plot of the residuals. (Make a histogram if your software does not make Normal quantile plots.) Is the distribution roughly Normal?

homes04