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(3 pts) Each of the following situations requires a significance test about a population mean . State the appropriate null hypothesis H 0 and alternative
- (3 pts) Each of the following situations requires a significance test about a population mean . State the appropriate null hypothesis H0 and alternative hypothesis Ha in each case:
a. Census Bureau data shows that the mean household income in the area served by a shopping mall is $72,500 per year. A market research firm questions shoppers at the mall to find out whether the mean household income of mall shoppers is higher than that of the general population.
b. Last year, your company's service technicians took an average of 1.8 hours to respond to trouble calls from business customers who had purchased service contracts. Do this year's data show a different average response time?
- (3 pts)The Survey of Study Habits and Attitudes (SSHA) is a psychological test that measures the motivation, attitude toward school, and study habits of students. Scores range from 0 to 200, with 200 being the highest level of motivation. The mean score for U.S. college students is about 115, and the standard deviation is about 30. A teacher who suspects that older students have better attitudes toward school gives the SSHA to 20 students who are at least 30 years of age.
- State the null and alternative hypotheses.
- The mean of her sample is 116.Calculate the z-statistic.
- Report the P-value of your test, and state your conclusion clearly: was the teacher justified in her suspicion.
- (4 pts) A bus company advertised a mean time of 150 minutes for a trip between two cities. A consumer group had reason to believe that the mean time was more than 150 minutes. A sample of 40 trips showed a mean x= 153 minutes and a standard deviation s=7.5 minutes. At the .05 level of significance, test the consumer group's belief.
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