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Unformatted text preview: are estimated from the sample. iv) It has millions of tickets, 66% marked "1"and 34% marked"0". c) Calculate the SE of the sample percent. Show work, circle answer. (Round to 2 decimal places.) i) First find the SD of the sample. SD = 0.66 × 0.34 =0.47 ii) Then use it to estimate the SD of the whole population in the SE% formula (Round to nearest tenth): SE% = SD of box/ € n x 100% (In public opinion polls the SE is usually between 1 ­2%) 0.47 SE% = × 100% = 1.16% rounds to 1.2% 1659 € € Page 11 Study Guide KEY for Exam 3 d) Your best estimate for the % of all American adults who think money and wealth should be more evenly distributed is ________66%___________, give or take about ___1.2%_____. (Fill in the first blank with the EV% and the second with the SE%) e) You can be 95% sure that if you polled all US adults the % who would answer that money and wealth should be more even distributed would be between 66% +/ ­ ___2.4%____ which means between ___63.6___________% and _____68.4_________%. Put lower number first. f) You can be 99% sure that if you polled all US adults the % who would answer that money and wealth should be more even distributed would be between 66% +/ ­ 3.12%_______ which means between ____62.88__________% and ____69.12__________%. Put lower number first. 99% CI =66% +/ ­ 2.6 x 1.2% = 66 % +/ ­ 3.12% 66%  ­3.12% = 62.88% and 66% +3.12% = 69.12% g) Suppose the poll was only taken in Illinois (instead of nationwide), how should CBS adjust the sample size to keep the same SE? i) Significantly increase sample size ii) Significantly decrease sample size iii) Keep sample size about the same. h) Suppose 1000 pollsters each randomly sampled 1,650 adults nationwide asking whether they thought money and wealth in this country should be distributed more evenly or whether it is fair the way it is now. All 1000 pollsters computed 90% confidence intervals to estimate the percentage of all US adults who thought money and wealth in this country should be distributed more evenly. Would all 100 intervals correctly include the true population percent? Choose one: i) Yes, all 1000 would assuming no errors were made ii) No, only about 80% of them would iii) No, only about 90% of them would. Page 12 Study Guide KEY for Exam 3 3) The figure shows the results of a computer simulation: 100 imaginary experimenters each tossed the same coin 100 times to determine whether or not it was...
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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.

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