Quiz 4.1A AP Statistics

For each of the following situations involving sampling, identify—as precisely as possible— the population that the sample represents. (a) A business school researcher wants to know what factors affect the survival and success of small businesses. She selects a sample of 150 eating-and-drinking establishments from those listed in the telephone directory for a large city. (b) A member of Congress wants to know whether his constituents support proposed legislation on health care. His staff reports that 228 letters have been received on the subject, of which 193 oppose the legislation. 2. A local radio talk-show host asks viewers to call in and vote for or against a proposed plan to raise the prices charged by municipal parking meters in a downtown shopping district. 75% of the respondents are opposed to the increase. Describe one possible source of error or bias that might arise in this poll and indicate the direction in which the estimate might be biased. What is the name for this kind of bias? 3. Two different organizations conduct polls in a city whose mayor has been accused of taking bribes. One poll asks a SRS of city residents, ―Do you think the mayor should resign because of accusations of his criminal activity?‖ The other asks, ―Do you think the mayor should resign?‖ The first poll concluded that the majority of city residents think the mayor should resign. The second poll drew exactly the opposite conclusion. Explain why their results might be so different. © 2011 BFW Publishers The Practice of Statistics, 4/e- Chapter 4 161 4. Your school will send a delegation of 35 seniors to a student life convention. 200 girls and 150 boys are eligible to be chosen. If a sample of 20 girls and separate sample 15 boys are each selected randomly, it gives each senior the same chance to be chosen to attend the convention. (a) Is it an SRS? Explain. (b) Beginning at line 108 in the random digits table, reproduced below, select the first three senior girls to be in the sample. Explain your procedures clearly. 108 60940 72024 17868 24943 61790 90656 87964 18883 109 36009 19365 15412 39638 85453 46816 83485 41979 110 38448 48789 18338 24697 39364 42006 76688 08708 162 The Practice of Statistics, 4/e- Chapter 4 © 2011 BFW Publishers Quiz 4.1B AP Statistics Name: 1. For each of the following situations involving sampling, identify—as precisely as possible— the population that the sample represents. (a) An insurance company wants to monitor the quality of its procedures for handling loss claims from its auto insurance policyholders. Each month the company selects an SRS of all auto insurance claims filed that month to examine them for accuracy and promptness. (b) A college admissions officer wants to know what the most important factors are that high school seniors consider when they choose where to apply to college. She conducts a telephone survey with a simple random sample of all applicants to her college. 2. In late 1995, a Gallup survey reported that about 46% Americans approved of sending troops to Bosnia. The poll did not mention that 20,000 U.S. troops were committed to go. A CBS News poll mentioned the 20,000 figure and got a different outcome—an approval rate of only 33%. Briefly explain why the mention of the number of troops would cause such a big difference in the poll results. Write the name of the kind of bias that is at work here. 3. A church group interested in promoting volunteerism in a community chooses an SRS of 200 community addresses and sends members to visit these addresses during weekday working hours to inquire about the residents’ attitudes toward volunteer work. Sixty percent of all respondents say that they would be willing to donate at least an hour a week to some volunteer organization. Bias is present in this sample design. Identify the type of bias involved and state whether you think the sample percent obtained is higher or lower than the true population percent. © 2011 BFW Publishers The Practice of Statistics, 4/e- Chapter 4 163 4. Each state conducts an annual study of seat belt use by drivers following guidelines set by the federal government. Seat belt use is observed at randomly chosen road locations at random times during daylight hours. The locations are based on counties within each state. In Hawaii, the counties are the islands that make up the state’s territory, and the survey is conducted on the 4 most populated islands: Oahu, Maui, Hawaii (referred to as ―The Big Island‖), and Kauai. The sample sizes on the islands are proportional to the amount of road traffic., so each location is equally likely to be selected. (a) Is this a SRS of road locations in the state of Hawaii? Explain. (b) Suppose there are 476 possible road locations on Kauai and we need to randomly select 22 of them to be in the sample. Beginning at line 120 in the random digits table below, choose the first 3 road locations for the seat belt survey sample. Explain your method clearly. 120 35476 55972 39421 65850 04266 35435 43742 11937 121 71487 09984 29077 14863 61683 47052 62224 51025 122 13873 81598 95052 90908 73592 75186 87136 95761 164 The Practice of Statistics, 4/e- Chapter 4 © 2011 BFW Publishers Quiz 4.1C AP Statistics Name: 1. The school’s newspaper has asked you to contact 100 of the approximately 1100 students at the school to gather information about student opinions regarding food at your school’s cafeteria. (a)With as much precision as possible, describe the population for your study. (b) You are pretty sure that there is a big difference between the opinions of males and females when it comes to cafeteria food. Describe a study design that takes into account this potentially important variable. Explain the advantage of this method. (c)You decide to conduct a survey about the quality of food served in the school cafeteria by randomly selecting students as they leave the cafeteria after lunch on a specific day next week. Describe a source of bias that may result from using this method. Be sure to use the correct terminology, and indicate the direction of the potential bias.