Chapter 7 and 8 Suggested Problems

Chapter 7

1. For each of the following sampling plans, indicate why the target population and the sampled population are no the same.

a) In order to determine the opinions and attitudes of customers who regularly shop at a particular mall, a surveyor stands outside a large department store in the mall and randomly selects people to participate in the survey.

b) A library wants to estimate the proportion of its books that has been damaged. The librarians decide to select one book per shelf as a sample by measuring 12 inches from the left edge of each shelf and selecting the book in that location.

c) Political surveyors visit 200 residences during one afternoon at ask eligible voters present in the house at the time whom they intend to vote for.

2. A statistician would like to conduct a survey to ask people their views on a proposed new shopping mall in their community. According to the latest census, there are 800 households in the community. The statistician has numbered each household (from 1 to 800) and she would like to randomly select 25 of these households to participate in the study. Use Minitab to generate the sample.

3. The operations manager of a large plant with four departments wants to estimate the person-hours lost per month due to accidents. Describe a sampling plan that would be suitable for estimating the plant-wide loss and for comparing departments.

4. Work Exercise 7.26 from your Barnes text

5. Work Exercise 7.27 from your Barnes text

Chapter 8

Note for Data_ch8: Go through hyperlink to data file Data_ch8. Save the file as "html" to your floppy disc. Open the file in Excel 97. Save the file as an Excel 97 file. Copy the data for each problem into Minitab and calculate the answers.

6. In a survey conducted to determine the cost of vacations, 63 individuals were randomly sampled. Each person was asked to compute the cost of his or her most recent vacation. The data is stored in Data_ch8. Assuming the standard deviation is $400, estimate with 95% confidence the average cost of vacations.

7. As part of a project to develop better lawn fertilizers, a research chemist wanted to determine the mean weekly growth rate of Kentucky Bluegrass, a common type of grass. A sample of 250 blades of grass was measured, and the amount of growth in one week was recorded. These produced an x-bar of .89.

1. Assuming that weekly growth is normally distributed with a standard deviation of .10 inches, estimate with 99% confidence the mean weekly growth of Kentucky Bluegrass.
2. Briefly interpret what the interval estimate tells you about the growth of Kentucky bluegrass.

8. A medical statistician wants to estimate the average weight loss of people who are on a new diet plan. In a preliminary study, he found that the smallest weight loss was three pounds and the largest weight loss was 39 pounds. How large a sample should he take to estimate the mean weight loss to within two pounds, with 90% confidence?