A survey of Internet users reported that 17% downloaded music onto their compute

Question

A survey of Internet users reported that 17% downloaded music onto their computers. The filling of lawsuits by the recording industry may be a reason why this percent has decreased from the estimate of 29% from a survey taken two years before. Suppose we are not exactly sure about the sites 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 sues are 1000. (ii) Both sample sues are 1600. (iii) The sample size for the survey reporting 29% is 1000 and the sample site for the survey reporting 17% a 1600. Summarize the effects of the sample sites on the results. We see in (i) and (ii) that smaller samples result in smaller z (stronger evidence) and wider intervals. While larger samples have the reverse effect. The results of (iii) show that the effec

Explanation / Answer

1) as p1=0.17 ; n1=1000 ; p2=0.29 ; n2=1000

hence std error of difference =(p1(1-p1)/n1+p2(1-p2)/n2)1/2

=0.0186

for 95% CI, z=1.96

hence confidence interval =(p2-p1) -/+ z*std error =0.0835 ; 0.1565

2)

confidence interval =(p2-p1) -/+ z*std error =0.0911 ; 0.1489

3)

confidence interval =(p2-p1) -/+ z*std error =0.0864 ; 0.1536

4)option 3 is correct

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