SOLUTION: A simple random sample is to be drawn from a population of 1200, in order to have 90%confidence that the sampling error in estimating "n"is no more the 0.03, what sample size will

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Question 92338: A simple random sample is to be drawn from a population of 1200, in order to have 90%confidence that the sampling error in estimating "n"is no more the 0.03, what sample size will be necessary?
P.S. I just ca not get this one and I have tryed.
Answer by stanbon(75887) About Me  (Show Source):
You can put this solution on YOUR website!
A simple random sample is to be drawn from a population of 1200, in order to have 90%confidence that the sampling error in estimating "n"is no more the 0.03, what sample size will be necessary?
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Since E=z'[sigma/sqrt(n)]
n=[z'/E]^2
Your Problem:
n=[1.645*sigma/0.03]^2
n = [1.645/0.03]^2 *sigma^2
n = 3006*sigma^2
Comment: You would have to know sigma to arrive at "n".
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Cheers,
Stan H.