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Unformatted text preview: rces of bias? Circle “Yes” or “No”. a) Selection bias i) Yes ii) No b) Non
response bias (not everyone who is selected responds.) i) Yes ii) No c) Response bias (response bias deals with how the questions are phrased). i) Yes ii) No 2) A Fox News poll asked a randomly selected sample of 1,015 adults nationwide the following question: “Do you personally believe in the existence of Hell?” I asked this class the same question on Bonus Survey 3 last semester. Here are the results. Yes No Sample Size Fox random poll 74% 26% 1,015 Bonus Survey 3 54% 46% 546 a) Which survey gives a better estimate of the percentage of all US adults who would say “YES”, they believe in hell? Circle one: i)
The Fox survey because the sample was randomly selected from the entire US adult population. ii)
The Fox survey because the sample size is larger. iii) The Bonus Survey because it was anonymous. iv) The Bonus Survey because people who watch Fox news are not representative of the population as a whole. b) The SE of the percentage of people in the Fox sample who answered, "YES" is closest to… Choose one: .74 * .26
i) 1, 015 * .74 * .26 *100% ii)
*100%
1, 015 € iii) Impossible to compute a SE for this sample because it can’t be translated into a box model.
€
€ Page 9 Study Guide KEY for Exam 3 3) Right before the last election www.cnn.com conducted a “quick vote” where they posted the question below on their website and allowed all internet users to cast their votes. Here are the results. : a) If we wanted to use this survey to estimate how all US adults would have answered this question at the time what
most closely resembles the relevant box model?
Circle one:
i)
It has 12,624 tickets; 14% marked “Cindy” and 86% marked “Michelle” ii)
It has millions of tickets marked with “1”s and “0”s. The exact percentages are unknown but are estimated from the sample. iii)
A box model is not appropriate for this poll because the sample was not randomly selected. b) Does the sample have selection bias? Circle one: i) Yes ii) No c) What is the SE for the percent of all US adults who would answer “Cindy McCain”?
(.14 )(.86)
x100% ii) 12, 624 x (.14)(.86)
i)
iii) Impossible to compute a SE for this sample.
12, 624
€
€ Chapter 17
Using Sample Percents to Estimate Population Percents and Building Confidence Intervals around the estimate. • The sample percent is used to estimate population percent and a margin of erro...
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This note was uploaded on 12/26/2012 for the course STAT 100 taught by Professor Kim during the Spring '08 term at University of Illinois, Urbana Champaign.
 Spring '08
 Kim
 Statistics

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