Amazon.com has become one of the most successful online merchants. Two measures of its success are sales and net income/loss figures. The data can be found in the file Amazon (source: Wikinvest, www.wikinvest.com).

a. Produce a scatter plot for Amazon’s net income/loss and sales figures for the period 1995–2015.

Determine the order (or degree) of the polynomial that could be used to predict Amazon’s net income/

loss using sales figures for the period 1995–2015.

b. Produce the polynomial model indicated by these data.

c. Test to determine whether the overall model from part b is statistically significant. Use a significance level of 0.10.

d. Conduct a hypothesis test to determine if curvature exists in the model that predicts Amazon’s net income/loss using sales figures from part

b. Use a significance level of 0.02 and the test statistic approach.

The following information applies to Exercises 15-67, 15-68, and 15-69.

A publishing company in New York is attempting to develop a model to help predict textbook sales for books it is considering for future publication. The marketing department has collected data on several variables from a random sample of 15 books. These data are given in the file Textbooks.