<p>Sampling - Solutions</p><p>Activity 1</p><p> Non-response bias refers to a bias that occurs if people with a particular opinion or trait tend to refuse to answer certain survey questions (or possibly refuse to participate in the survey at all). </p><p> Response bias refers to the systematic effect of false answers given by survey participants. Suppose the office that does the Penn State Pulse surveys does a survey about the frequency of academic cheating (and they have!). In the context of such a survey about cheating, explain the difference between nonresponse bias and response bias.</p><p>Non-response: perhaps those who cheat a lot won’t answer questions, or will refuse to be in the survey. Response: perhaps those who cheat a lot will lie about their cheating.</p><p>Activity 2 Suppose you want to sample the music of a band you haven’t heard before. You’re given 5 CDs, each with 12 tracks. You’ll use a probability method to sample 5 tracks to play. a. Describe (briefly) how you would carry out a simple random sampling method to pick the 5 tracks. </p><p>Number the 60 total tracks from 1 to 60. Randomly pick 5 numbers between 1 and 60. Listen to those tracks. (The “random shuffle” button of a 5 cd player might accomplish this) b. Describe (briefly) how you would carry out a stratified sampling method to pick the 5 tracks.</p><p>The strata = CD’s. Randomly pick one track from each CD. c. Describe briefly how you would carry out a cluster sampling method to pick the 5 tracks.</p><p>Clusters = CD’s. Perhaps randomly pick one CD and then randomly pick 5 tracks from this CD, or randomly pick all the same track number.</p><p>Activity 3 Suppose that a study of 1009 students shows that students who got at least 7 hours of sleep per night during a semester had a higher average GPA than students who slept less. a. Calculate the “conservative” margin of error for this study. Express the answer as a percent. Calculate the “conservative” margin of error for this poll. Express the answer as a percent. 1  .031, so about 3% 1009 b. Is it more likely that this is an observational study or an experiment? Explain. Observational. Almost certainly the researchers did a survey, and did not assign amounts of sleep to the students.</p><p>1 c. In this study, what variable is the explanatory variable and what variable is the response variable? Explanatory = sleep response = GPA d. Which of the following variables are likely to be lurking variables in this study? Explain why in each case.</p><p>Number of courses the student took that semester Probably confounded because it would affect both sleep and GPA. Weight of the student Probably not confounded – doubtful that it affects either sleep or GPA</p><p>Number of hours the student spent partying in a typical week Might be confounded because it could affect both sleep and GPA.</p><p>2</p>