# STATISTIC

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A survey of Internet users reported that 21% 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.)

(i) Both sample sizes are 1000.
z = ____________

(ii) Both sample sizes are 1600.
z = _____________

(iii) The sample size for the survey reporting 31% is 1000 and the sample size for the survey reporting 21% is 1600.

z = _____________

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