1. A study by Experian found that 20% of consum- ers in New Jersey have 10 or more credit cards, com- pared to 11% in Tennessee. In a two-tail test at the 0.05 level of significance, and assuming the percentages are from independent samples of 100 consumers each, can we conclude that New Jersey and Tennessee consumers might not differ in terms of the percentage who have 10 or more credit cards? Determine and interpret the p-value for the test, then construct and interpret the 95% confidence interval for the difference between the population proportions. Source: "1 in 7 Americans Carry 10 or More Credit Cards," moneycentral.msn.com, July 25, 2009.
2. Given the information in Exercise 11.75, and using the 0.05 level of significance in comparing the sample standard deviations, were we justified in assum- ing that the population standard deviations were equal? Would your conclusion change if the standard deviation of the estimates received by Emily had been $35?