A survey of Internet users reported that 15% downloaded music onto their computers. The filing of lawsuits by the recording industry may be a reason why this percent has decreased from the estimate of 31% from a survey taken two years before. Suppose we are not exactly sure about the sizes of the samples. Perform the calculations for the significance tests and 95% confidence intervals under each of the following assumptions. (Use previous − recent. Round your test statistics to two decimal places and your confidence intervals to four decimal places.) (iii) The sample size for the survey reporting 31% is 1000 and the sample size for the survey reporting 15% is 1600. z=
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31 - 0.15 = 0.16 Show more…
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132. Public Policy Polling recently conducted a survey asking adults across the U.S. about music preferences. When asked, 80 of the 571 participants admitted that they have illegally downloaded music. a. Create a 99% confidence interval for the true proportion of American adults who have illegally downloaded music. b. This survey was conducted through automated telephone interviews on May 6 and 7, 2013. The error bound of the survey compensates for sampling error, or natural variability among samples. List some factors that could affect the survey's outcome that are not covered by the margin of error. c. Without performing any calculations, describe how the confidence interval would change if the confidence level changed from 99% to 90%.
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Public Policy Polling recently conducted a survey asking adults across the U.S. about music preferences. When asked, 80 of the 571 participants admitted that they have illegally downloaded music. a. Create a 99% confidence interval for the true proportion of American adults who have illegally downloaded music. b. This survey was conducted through automated telephone interviews on May 6 and 7, 2013 . The error bound of the survey compensates for sampling error, or natural variability among samples. List some factors that could affect the survey's outcome that are not covered by the margin of error. c. Without performing any calculations, describe how the confidence interval would change if the confidence level changed from 99% to 90%.
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