Question

A survey of Internet users reported that 18% 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 25% from a survey taken two years before. Assume that the sample sizes are both 1361. Using a significance test, evaluate whether or not there has been a change in the percent of Internet users who download music. Provide all details for the test. (Round your value for z to two decimal places. Round your P-value to four decimal places.)

Z=

P-value=

Also report a 95% confidence interval for the difference in proportions. (Round your answers to four decimal places.

Answer 1

Proportion of student who downloaded before, = 0.25

Proportion of student who downloaded after, = 0.18

n1=n2 = 1361

Null and alternative hypothesis:

Test statistic:

P-value = 0.0000

Conclusion:

As p-value=0 <0.05, reject the null hypothesis.

There is enough evidence to claim that there has been a change in the percent of Internet users who download music.

At = 0.05, critical value of = ABS(NORM.S.INV(0.05/2)) = 1.96

95% confidence interval for the difference in proportions: