Question

The authors of a paper concluded that more boys than girls listen to music at high volumes. This conclusion was based on data from independent random samples of 768 boys and 745 girls from a country, age 12 to 19. Of the boys, 397 reported that they almost always listen to music at a high volume setting. Of the girls, 331 reported listening to music at a high volume setting.

Do the sample data support the authors' conclusion that the proportion of the country's boys who listen to music at high volume is greater than this proportion for the country's girls? Test the relevant hypotheses using a 0.01 significance level. (Use a statistical computer package to calculate the P-value. Use μboys − μgirls. Round your test statistic to two decimal places and your P-value to four decimal places.)

Answer 1

Since the calculated value of z= 2.82 does not lie in the critical region the null hypothesis is accepted and it is concluded that the sample data support the authors' conclusion that the proportion of the country's boys who listen to music at high volume is greater than this proportion for the country's girls.

The value of p is 0 .00233. The result is significant at p < 0.10.

Explanation:

1) Let the null and alternate hypothesis be

H0: μboys − μgirls > 0

against the claim

Ha: μboys − μgirls ≤ 0

2) The significance level is set at 0.01

3) The critical region is z ≤ ± 1.28

4) The test statistic

Z= p1-p2/ sqrt [pcqc( 1/n1+ 1/n2)]

Here p1= 397/768= 0.5169 and p2= 331/745=0.4429

pc = 397+331/768+745

pc= 0.4811

qc= 1-pc= 1-0.4811=0.5188

5) Calculations

Z= p1-p2/ sqrt [pcqc( 1/n1+ 1/n2)]

z= 0.5169-0.4429/√ 0.4811*0.5188( 1/768+ 1/745)

z= 2.82

6) Conclusion

Since the calculated value of z= 2.82 does not lie in the critical region the null hypothesis is accepted and it is concluded that the sample data support the authors' conclusion that the proportion of the country's boys who listen to music at high volume is greater than this proportion for the country's girls.

7)

The value of p is 0 .00233. The result is significant at p < 0.10.