SOLUTION: A researcher wishes to estimate within $25 the average cost of postage a community college spends in one year. If she wishes to be 90% confident, how large of a sample will be nece

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Question 1161757: A researcher wishes to estimate within $25 the average cost of postage a community college spends in one year. If she wishes to be 90% confident, how large of a sample will be necessary if the population standard deviation is $80.

Answer by Lavanya gupta(1) About Me  (Show Source):
You can put this solution on YOUR website!
Solution:
Given, A researcher wisher to estimate within $25 i.e. E=25
population standard deviation sigma=$80
90% confident Z=1.645
now, sample size n=%28z%2Asigma%2Fsqrt+n%29%5E2
n=(1.645*80/25)^2 = (5.264)^2 =27.7097
=28
Therefore, sample size n=28