Question 11.19

11.19 Predicting the price of tablets: Individual variables.

Suppose your company needs to buy some tablets. To help in the purchasing decision, you decide to develop a model to predict the selling price. You decide to obtain price and product characteristic information on 20 tablets from Consumer Reports.6 The characteristics are screen size, battery life, weight (pounds), ease of use, display, and versatility. The latter three are scored on a 1 to 5 scale.

tablts

  1. Make a table giving the mean, median, and standard deviation of each variable.
  2. Use stemplots or histograms to make graphical summaries of each distribution.
  3. Describe these distributions. Are there any unusual observations that may affect a multiple regression? Explain your answer.
  4. The screen size distribution appears bimodal. Is this lack of Normality necessarily a problem? Explain your answer.

11.19

(a)

Variable Mean Median Std Dev
Price 395.50 400.00 119.76
Size 9.15 9.90 1.21
Battery 11.11 10.55 2.57
Weight 1.07 1.10 0.29
Ease 4.55 5.00 0.51
Display 4.30 4.00 0.47
Versatility 3.80 4.00 0.41

(c) Price is roughly Normal. Size has a bimodal distribution. Battery is right-skewed. Ease, Display and Versatility all only have 2 different values even though they were rated on a 1 to 5 scale. There aren’t really any unusual observations that might affect the regression analysis. (d) No, we do not make any assumption on the distribution of explanatory variables, so this is perfectly fine.