A market researcher is studying on line subscription services. She is particularly interested in what variables relate to the number of subscriptions for a particular on line service. She is able to obtain the following sample information on 25 on line subscription services. The following notation is used:

Sub = Number of subscriptions (in thousands)

Web page hits = Average monthly count (in thousands)

Adv = The advertising budget of the service (in $ hundreds)

Price = Average monthly subscription price ($)

a. Determine the regression equation.

b. Conduct a global test of hypothesis to determine whether any of the regression coefficients are not equal to zero.

c. Conduct a test for the individual coefficients. Would you consider deleting any coefficients?

d. Determine the residuals and plot them against the fitted values. Do you see any problems?

e. Develop a histogram of the residuals. Do you see any problems with the normality assumption?

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Web Page Service Sub Hits Adv Price 1 37.95 588.9 13.2 35.1 2 37.66 585.3 13.2 34.7 37.55 566.3 19.8 34.8 23 38.83 629.6 22.0 35.3 24 38.33 680.0 24.2 34.7 25 40.24 651.2 33.0 35.8 ... ....