You have just completed your business statistics course and are shopping for a laptop computer at Best Buy. To help you with your decision, you decide to construct a regression model to predict the selling price of the laptop. The Excel file laptops.xlsx provides the following data for a random sample of laptops on Best Buy’s Web site:

• Selling price

• Brand

• Screen size (in.)

• Hard drive size (GB)

• Amount of RAM memory (GB)

• Number of USB ports

• Weight (oz.)

a. Check for the presence of multicollinearity between the independent variables. If it is present, take the necessary steps to eliminate it.

b. Construct a regression model using all the independent variables remaining after part a.

c. Test the significance of the overall regression model from part a using α = 0.05.

d. Construct a regression model using best subsets regression to predict the price of a laptop using the independent variables from part b.

e. Interpret the meaning of each of the regression coefficients with the model from part d.

f. Construct a 95% confidence interval for the regression coefficients for the size variable from part d. Be sure to interpret the meaning of this confidence interval.

g. Predict the price of a Toshiba laptop with a 15.6 in. screen, 4 GB of RAM memory, a 500 GB hard drive, and three USB ports that weigh 5.2 ounces.

h. Use PHStat to construct a 95% prediction interval for the laptop described in part g and interpret its meaning.