Suppose last year, a sample of 180 freshman showed 65% of them used the local bo
ID: 3181235 • Letter: S
Question
Suppose last year, a sample of 180 freshman showed 65% of them used the local bookstore to get their semester textbooks. This year, 60% of a sample of 170 them use the local bookstore.
(a) Is there significant evidence that the percentage has decreased? Conduct an appropriate test with = .05, defining any parameters used.
(b) If the percentage last year was not based on a sample but in fact the percentage among all freshman, explain how the test in part (a) would be different. Carry out the test in this case.
Explanation / Answer
here p1=0.65 ; n1=180
p2=0.6 ; n2=170
from above std error of difference =(p1(1-p1)/n1+p2(1-p2)/n2)1/2 =0.0517
hence test stat z =(p1-p2)/std errror =0.9666
for above p value =0.3337
as p value is greater then 0.05 we can not reject that both mean are equal.
b)here p=0.65
and phat =0.6
std error =(p(1-p)/n)1/2 where n=170
=0.0366
hence test stat z=(phat-p)/std error =-1.3668
for above p value =0.1717
as p value is greater then 0.05 we can not reject that both mean are equal.