3. [-/0.27 Points] DETAILS BBUNDERSTAT12 7.4.013.S. MY NOTES ASK YOUR TEACHER PRACTICE ANOTHER For large U.S. companies, what percentage of their total income comes from foreign sales? A random sample of technology companies (IBM, Hewlett-packard, Intel, and others) gave the following information.+ Technology companies, % foreign revenue: x, ; n, = 16 62.8 55.7 47.0 59.6 55.3 41.0 65.1 51.1 53.4 50.8 48.5' 44.6 49.4 61.2 39.3 41.8 Another independent random sample of basic consumer product companies (Goodyear, Sarah Lee, H.J. Heinz, Toys 'R' Us) gave the following information. Basic consumer product companies,% foreign revenue: x,; n, = 17 28.0 30.5 34.2 50.3 11.1 28.8 40.0 44.9 40.7 60.1 23.1 21.3 42.8 18.0 36.9 28.0 32.5 LO USE SALT Assume that the distributions of percentage foreign revenue are mound-shaped and symmetric for these two company types. (a) Use a calculator with mean and standard deviation keys to calculate x], $1, X2, and $2. (Round your answers to four decimal places.) S , 0/% X 2 (b) Let , be the population mean for x, and let /2 be the population mean for x2. Find a 90% confidence interval for 1 - #2. (Round your answers to two decimal places.) lower limit upper limit % (c) Examine the confidence interval and explain what it means in the context of this problem. Does the interval consist of numbers that are all positive? all negative? of different signs? At the 90% level of confidence, do technology companies have a greater percentage foreign revenue than basic consumer product companies? Because the interval contains both positive and negative numbers, we can not say that technology companies receive a higher percent of foreign revenue. Because the interval contains only negative numbers, we can say that technology companies receive a lower percent of foreign revenue. We can not make any conclusions using this confidence interval. Because the interval contains only positive numbers, we can say that technology companies receive a higher percent of foreign revenue. d) Which distribution (standard normal or Student's t) did you use? Why? Student's t was used because of and o, are known. Standard normal was used because o, and o2 are unknown. Standard normal was used because of and 62 are known. Student's t was used because of and o are unknown. Need Help? Read it Watch It