Chapter 5 Review Sampling & Experimental Design

Unit 4 Review – Sampling & Experimental Design Chapters 11-13

1) A large elementary school has 15 classrooms with 24 children in each classroom. A sample of 30 children is chosen by the following procedure: Each of the 15 teachers selects 2 children from his or her classroom to be the sample by numbering the children from 1 to 24, then using a random number table to select two different random numbers from 01 to 24. The two children with those numbers are the sample. Does this procedure give a simple random sample of 30 children from the elementary school? A) No, because the teachers were not selected randomly. B) No, because not all possible groups of 30 children had the same chance of being chosen. C) No, because not all children had the same chance of being chosen. D) Yes, because each child had the same chance of being chosen. E) Yes, because the numbers were assigned randomly to the children.

2) Out of large shipment of fuses received from a new supplier, a manufacturer selects and tests 100 fuses. On the basis of the test, the manufacturer decides to accept this particular shipment. In arriving at this decision the manufacturer interpreted A) the fuses tested and the shipment both as samples B) the fuses tested and the shipment both as populations C) the fuses tested as a sample and the shipment as a population D) the fuses tested as the population and the shipment as the sample E) the notions of samples & populations do not apply in this context

3) Which of the following does not truly represent a possible advantage of sampling over census? A) One can collect data more quickly with a sample B) One can collect data more cheaply with a sample C) With a sample, one will obtain data that is more symmetric D) Under some conditions, such as destructive sampling, sampling is the only practical way to collect data. E) A through D all represent advantages of sampling over taking a census

4) In a survey of public opinion concerning state aid to a particular city, every 40th person registered as a voter was interviewed, beginning with a person selected at random from among the first 40 listed. This is an example of: A) Simple random sampling B) systematic sampling C) stratified sampling D) single-stage cluster sampling E) none of the above

5) Suppose that a number of crates of pencils is chosen at random from a boxcar of crates, and then a number of boxes of pencils is chosen at random from each selected crate. Our goal is to determine the number of defective pencils in a box. This is an example of: A) single-stage cluster sampling B) multi-stage cluster sampling C) stratified sampling D) systematic sampling E) none of these 6) A sample selected in such a manner that each sample of size n has the same probability of being selected is: A) a convenience sample B) a judgment sample C) non-probabilistic sample D) a simple random sample E) none of the above

7) In the 1992 presidential election, about 68% of the voting-age population registered to vote and about 61% actually voted. Just after the election, you ask a random sample of adults whether or not they voted. Do you expect bias? That is, do you expect about 61%, less than 61%, or more than 61% of the sample to claim they voted? Explain your answer.

8) Margin O’Error has a small accounting firm, which serves 30 clients. Margin wants to interview a sample of 6 of them in detail to find ways to improve client satisfaction. To avoid bias she wants to choose a simple random sample. Below is a list of the clients and a section of the random number table. Explain how you will assign numbers to the clients and then mark on or above the table to demonstrate how you arrived at your SRS of size 6.

A-1 Plumbing Classic Flowers Peerless Machine Accent Printing Computer Answers Photo Arts Action Sport Shop Darlene’s Dolls River City Books Anderson Construction Fleisch Realty Riverside Tavern Bailey Trucking Hernandez Electronics Rustic Boutique Balloons Inc. Johnson Commodities Satellite Services Bennett Hardware JL Records Scotch Wash Best’s Camera Shop Keiser Construction Sewer’s Center Blue Print Specialties Liu’s Chinese Restaurant Tire Specialties Central Tree Service Magic Tan Von’s Video Store

69015 64817 87174 09517 84534 06489 87201

97245 05007 16632 81194 14873 04197 85576

List your sample of six.

9) The list of individuals from which a sample is actually selected is called the sampling frame. Ideally, the frame should list every individual in the population, but in practice this is often difficult. A frame that leaves out a part of the population is a common source of under-coverage.

A) Suppose that a sample of households in Dallas is selected at random from the telephone directory. What households are omitted from the frame? What types of people are likely to be missed?

B) It is more common in telephone surveys to use random digit dialing equipment that selects the last four digits of the telephone number at random after being given the exchange (the first three digits). Which of the households mentioned in part A will now be included in the sampling frame? Will the survey still be biased? Explain. 10) The Grapevine Police Department is presently using three different makes of police cars and they currently have 120 cars. The department is interested in determining whether one of the four possible brands of gasoline gets better mileage than the rest. When you design the experiment… Will it be completely randomized or a block design? How many factors are there? How many treatments? If it is a block design, which characteristics are used as the blocking value? What would be the explanatory and response variables?

11) It is believed that 75% of all apartment dwellers in a large city deadbolt their doors in addition to locking them as an added precaution against burglary. A) Describe in detail how you would simulate a SRS of 20 apartment dwellers.

B) Using lines from the random digit table below, simulate a SRS of 20 apartment dwellers.

59636 88804 04634 71197 19352 73089 85898 45785 62568 70206 40325

03699 71080 22553 11486 11776 45149 32992 75730 66280 03819 56202

12) A large forest near an industrial area suffers from the effects of acid rain. It is estimated that 30% of all trees in the forest display some sign of acid rain damage.

A) Describe how you would use the random digit table below to simulate an SRS of 10 trees from the forest.

B) Use the random digits below to simulate a SRS of 10 trees. What is the proportion of trees in the sample that display some signs of acid rain damage?

13873 81598 85052 90908 73592 75186 87136 95761 54580 81507 27102 56027

13) A new drug to reduce blood pressure is being tested. We want to test the drug at three dosage levels, 10 mg, 20 mg, and 30 mg. It is also thought that combining this drug with regular exercise might help make it more effective so we want to include walking for 30 minutes a day as a treatment also. A) Design a completely randomized experiment with 400 subjects who suffer from high blood pressure (be sure to include a control group in your study).

B) What are the factors?

C) What are the experimental units?

D) How many treatments are there?