# Q-3a. a sample of students from an introductory psychology class were

**Q-3a.** A sample of students from an introductory psychology class were polled regarding the number of hours they spent studying for the last exam. All students anonymously submitted the number of hours on a 3 by 5 card. There were 24 individuals in the one section of the course polled. The data was used to make inferences regarding the other students taking the course. Construct a 95% confidence interval estimate . Explain your findings so that your non-quantitave partner will understand them. Their data is below: **(5 pts.)**

**20** **18** **7.5** **11** **10** **3.5** **7.5** **18** **19** **2.5** **9** **14**

**9** **14** **14.5** **17** **22** **4.5** **10.5** **15** **5** **8.5** **8** **20**

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**Q-3b.** A sample of Alzheimer’s patients are tested to assess the amount of time (in minutes) in stage IV sleep. It has been hypothesized that individuals sufferering from Alzheimer’s Disease may spend less time per night in the deeper stages of sleep. The number of minutes spent is Stage IV sleep is recorded for thirty patients (refer to sample data below of stage IV sleep over a 24 hour period). Compute a 95 percent confidence interval for this data. What does this information tell you about a particular individual’s (an Alzheimer’s patient) stage IV sleep? Explain your findings so that your non-quantitative partner will understand them. **(5 pts.)**

**Stage IV Sleep in Minutes**

**28.5** **37.4** **18.5** **53.2** **61.3** **18.75** **33.9** **27.1** **73.0** **53.4** **66.0** **20.5** **51.7** **57.25** **35.6**

**33.4** **25.1** **65.3** **55.0** **35.0** **19.25** **81.5** **44.1** **28.7** **36.5** **32.2** **47.3** **41.7** **39.75** **18.3**

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**Q-3c**. A large retail corportation plans to sample sales receipts of its meat department to estimate the average size (in dollars) of a customer purchase. Previous analysis suggest that the standard deviation of the purchase amount is approximately $50.72. In order to calculate a 95% confidence interval of the __ total__ width less than $6.50, how many sales receipts should the corportion include in the sample? Explain your findings so that your non-quantitative partner will understand them.

**(5 pts.)**

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**Q-3d.** A survey of 850 workers were asked how much they used the Internet at work. 578 said they used the internet within limits, and 255 said that they did not use the Internet within limits. Construct a 95% confidence interval estimate for the proportion of all workers who did not use the Internet within limits. Explain your findings so that your non-quantitative partner will understand them. **(5 pts.)**

__ _______________________________________________________________________________________________________________

**Q-3e.** You are the designer for your company’s web site. You have data to indicate that the mean download time for the homepage is 5.8 seconds and that the standard deviation of download time is 2.1 seconds. If we assume that the download times are normally distributed, what percent of users will wait between 4 and 8 seconds for the homepage to download? Explain your findings so that your non-quantitative partner will understand them. **(5 pts.)**

**Q-4a.** You are the manager of a popular retail store. You want to determine whether the population mean wait time for customer to

check-out has changed in the past month from its previous population mean value of 4.25 minutes. From past experience, you

can assume that the population is normally distributed with a population standard deviation of 1.6 minutes. You select a sample

of 43 customer’s wait time to check-out during a one hour period. The sample mean is 4.75 minutes. Determine whether there

is evidence at the 0.05 level of significance that the population mean wait time to check-out has changed in the past month from

its previous population mean value of 4.25 minutes. Explain your findings utlizing information from the hypothesis test you

conduct. **(5 pts.)**

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**Q-4b.** You are the manager of a fast-food restaurant. Based on a sample of two-hundred fifty drive-through orders, you discovered that

orders were filled correctly 86.5% of the time. In an effort to improve the amount of orders filled correctly, you developed a new

process to fill orders. After sampling two-hundred fifty orders under this new process, the results reviled that 225 orders were

filled correctly. At the 0.01 level of significance, can you conclude that the new process population proportion of orders filled

correctly is higher than the proportion of orders filled under the old process? Explain your findings utilizing information from the

test you conduct. **(5 pts.)**

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