A major Canadian retailer with stores only in large cities includes food items in some stores but not in others. Selling food requires refrigeration equipment, which considerably increases the electricity bill. It also increases water usage for washing fresh food. The retailer is investigating ways of reducing water and electricity usage, to reduce both operating costs and its environmental footprint. It wants to identify stores that have particularly low water and electricity usage as examples of what other stores might achieve and obtains two histograms:

The mean and standard deviations are:

a) Using z-scores, compare the following stores:

b) Describe the shapes of the histograms and the format in which they are drawn. What might the shapes imply? What should be the next step in analyzing this data? (You are not asked to perform this next step, just to say what it is.)

c) In order to select stores that have low water and electricity usage as an example to other stores, the company instructs its statisticians to select stores toward the left end of the two histograms. Comment on the ethics of this instruction using the ethical guidelines in Appendix C.

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Water 20 100 50 150 200 250 300 350 More Litres per sq. ft. per Year Electricity 40 20 600 300 900 1200 1500 1800 2100 2400 More Dollars per 1000 sq. ft. per Year Number of Stores Number of Stores Mean Standard Deviation Water (litres per sq. ft. per year) Electricity (dollars per 1000 sq. ft. per year) 124.37 79.38 956.78 565.66