A number of companies sell both cars and trucks in Canada. Do a company's car sales go up (or down) in tandem with its truck sales? The accompanying table shows the annual percent changes in car and truck sales for a selection of companies that offer both. Use the Wilcoxon signed-ranks test to test the hypothesis that there is no difference in a company's percent change in sales for cars and trucks. By its use of ranks, the Wilcoxon test is not sensitive to the magnitude of differences where they occur. Inspecting these data, would you be inclined to predict changes in car sales based on changes in truck sales?

Use a 0.05 significance level with the indicated test. If no particular test is specified, use the appropriate nonparametric test from this chapter.

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Car change 34.3 93.7 319 79.6 27.8 6.4 2.7 -20.8 Truck cha 24. 73 13.3 8.6 33.3 0 33.9 59.3 -19.4 Based on data in The Globe and Mail