9.13 THE VIDEO GAME SATISFACTION RATING CASE VideoGa ME. Recall that "very satisfied" customers give the XYZ-Box video game system a rating that is at least 42. Suppose that the manufacturer of the...

9.13 THE VIDEO GAME SATISFACTION RATING CASE VideoGa ME. Recall that "very satisfied" customers give the XYZ-Box video game system a rating that is at least 42. Suppose that the manufacturer of the XYZ-Box wishes to use the random sample of 65 satisfaction ratings to provide evidence supporting the claim that the mean composite satisfaction rating for the XYZ-Box exceeds 42. a Letting pe. represent the mean composite satisfaction rating for the XYZ-Box, set up the null hypothesis Ho and the alternative hypothesis H. needed if we wish to attempt to provide evidence supporting the claim that A exceeds 42, b The random sample of 65 satisfaction ratings yields a sample mean of = 42.954. Assuming that a- equals 2.64, use critical values to test Ho versus H. at each of a = .10, .05, .01, and .001. c Using the information in part b, calculate the p-value and use it to test 11,, versus H. at each of a = .01, and .001. d How much evidence is there that the mean composite satisfaction rating exceeds 42?
9.22 How do we decide whether to use a z test or a t test when testing a hypothesis about a population mean?
Chi-Square Goodness-of-Fit Tests
12.10 A wholesaler has recently developed a computerized sales invoicing system. Prior to implementing this system, a manual system was used. The distribution of the number of errors per invoice for the manual system is as follows:
Errors per Invoice 0 1 2 3 More Than 3 Percentage of Invoices 87% 8% 3% 1% 1% % After implementation of the computerized system, a random sample of 500 invoices gives the following error distribution:
Errors per Invoice • 0 Number of Invoices 479
10
2 3 More Than 3 8 2 1
a Show that it is appropriate to carry out a chi-square test using these data. b Use the following Excel output to determine whether the error percentages for the computerized system differ from those for the manual system at the .05 level of significance. What do you conclude?
pi Ei fi (1-E)^2/E 0.8? 435 479 4.4506 0.08 40 L0 22.5000 0.03 15 8 3.2667 0.01 5 2 1.8000 0.01 5 1 3.2000 Chi- 35.21724 p-value 0.0000001096 Square