# Sample Sale Receipts

Q-a. 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

Q-b. 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

Q-c. 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 corporation include in the sample? Explain your findings so that your non-quantitative partner will understand them. (5 pts.)

Q-d. 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.)