Hotels often leave questionnaires concerning the quality of their service in the hotel rooms and ask the guests to fill them out. The interviewer contacts the families that live in the nice section of town and reports that the other families could not be contacted. A student adviser wants to estimate the mean annual income of all university students who graduated last year. A random sample of 100 working people participated in a survey of workforce characteristics. For the following situation, indicate whether a correct decision has been made or if a Type I or Type II error has occurred.
New system is better.
A management firm would like to estimate the mean cost of repairing damage to apartments that are vacated by tenants. Two manufacturing companies produce carbide drill tips that are used to cut holes in steel sheets. The population variances are unknown but assum ed to be equal. A researcher honestly believes that a new medication reduces blood pressure. However, a test on five people did not show a significant average reduction in blood pressure.