Producing Data: Sampling BPS chapter 8 © 2010 W.H. Freeman and Company

Sampling In 1993, presidential candidate Ross Perot appeared on television to voice his opinions on government reform. To gauge public opinion, Perot urged viewers to fill out the survey appearing in that week’s issue of TV Guide. Of the approximately 1.4 million respondents, 98% agreed with Ross Perot’s platform on health care reform. What type of sampling method was used? a) Convenience sample b) Voluntary response sample c) Simple random sample d) Stratified sample e) Multistage sample

Sampling Which of the following is NOT a type of probability sample? a) Voluntary response sample b) Simple random sample c) Stratified sample d) Multistage sample e) All are probability samples.

Sampling Suppose you want to estimate the proportion of students at a large university that approve of the new health care bill. You take an SRS of 200 of the 25,000 undergraduate students and an SRS of the 100 of the 5,000 graduate students. This overall sample is a a) Voluntary response sample b) Simple random sample c) Stratified sample d) Multistage sample e) None of the above

Selecting a sample Select an SRS of 5 packages of peanuts form a case containing 30 packages of peanuts. Label the packages 01 to 30 and use the line from the table of random digits shown below. Your SRS contains the packages of peanuts labeled a) 14, 44, 45, 49, 92 b) 14, 26, 05, 14, 24 c) 14, 45, 92, 60, 56 d) 14, 03, 10, 22, 06 e) None of the above

Sampling Which of the following sampling schemes describes a multistage sample of 200 undergraduate students at a large university? a) Obtain a list of the undergraduate students at the large university; assign consecutive numbers to the students on the list; use a random number table to select 200 university students. b) Obtain a list of all freshmen, sophomores, juniors, and seniors; use a random number table to randomly select 50 students from each class. c) Randomly select 10 colleges; within each college, randomly select 5 majors; from each of the selected majors randomly select 4 undergraduate students.

Bias A Gallup poll sponsored by the disposable diaper industry asked “It is estimated that disposable diapers account for less than 2% of the trash in today’s landfills. In contrast, beverage containers, third- class mail, and yard waste are estimated to account for about 21% of the trash in landfills. Given this, in your opinion, would it be fair to ban disposable diapers?” Which type of bias does this poll suffer from? a) Under-coverage bias b) Non-response bias c) Response bias d) Question wording bias e) Interviewer bias

Bias True or false: Bias can occur in both probability and non-probability samples. a) True b) False

Bias Using a local telephone book to select a simple random sample could introduce what type of bias? a) Under-coverage bias b) Non-response bias c) Response bias d) Question wording bias e) Interviewer bias

Probability samples An important characteristic of probability samples is that a) Results of one sample are usually the same as the results for the entire population. b) Results of one sample are usually the same as the results for another sample of the same size. c) Principles of chance apply and the size of error due to sampling is measurable. d) Smaller samples give more accurate results than larger samples.

Bias If people tend to respond differently to a question depending on whether the interviewer is male or female, which type of bias is present? a) Under-coverage bias b) Non-response bias c) Response bias d) Question wording bias e) Interviewer bias