Question 961740: need help please
A group of investors wants to develop a chain of fast-food restaurants. In determining potential costs for each facility, they must consider, among other expenses, the average monthly electric bill. They decide to sample some fast-food restaurants currently operating to estimate the monthly cost of electricity. They want to be 99% confident of their results and want the error of the interval estimate to be no more than $100. They estimate that such bills range from $600 to $2,500. How large of a sample should they take?
need to show the work
Answer by stanbon(75887)   (Show Source):
You can put this solution on YOUR website! need help please
A group of investors wants to develop a chain of fast-food restaurants. In determining potential costs for each facility, they must consider, among other expenses, the average monthly electric bill. They decide to sample some fast-food restaurants currently operating to estimate the monthly cost of electricity. They want to be 99% confident of their results and want the error of the interval estimate to be no more than $100. They estimate that such bills range from $600 to $2,500. How large of a sample should they take?
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n = [z*s/E]^2
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Since the standard deviation is not given,
us 6*s = range = (2500-600) = 1900
Then s = 316.67
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Ans: n = [2.5758*316.67/100]^2 = 67 when rounded up
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Cheers,
Stan H.
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