Does past growth in a company translate to continued growth in the future? In 1988, Profit magazine identified the 50 fastest-growing companies in Canada. In 1998, it revisited these companies. Of the companies for which relevant data were available, 10 have been randomly selected. Compare their sales in 1987 and 1997 (in millions of dollars).
a. At the 0.05 significance level, test the claim that fast-growing companies do grow in sales after 10 years. Does the fact that some companies in the 1987 survey went out of business or would not report their sales for 1997 affect the validity of the sample? (Consider the issues raised in Section 1-3.)
b. Construct a 95% confidence interval for the mean of the difference between 1987 sales and 1997 sales.

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Company A BC DE FGH I 1987 Sales 1.0 1.0 3.1 2.7 4.2 7.8 7.6 2.07.0 6.0 1997 Sales 5.0 2.5 17 4.5 19.0 17.0 17.0 1.2 64.0 8.0