SOLUTION: You are trying to estimate the average amount a family spends on food during a year. In the past, the standard deviation of the amount a family spends on food during the year has

Question 353762: You are trying to estimate the average amount a family spends on food during a year. In the past, the standard deviation of the amount a family spends on food during the year has been approximately $1,500
a. If you want to be 95% sure that you have estimated average family food expenditures within $100, how many families do you need to survey?
b. How many do you need to survey if you want to be 99% sure?

Answer by stanbon(75887) (Show Source): You can put this solution on YOUR website!
You are trying to estimate the average amount a family spends on food during a year. In the past, the standard deviation of the amount a family spends on food during the year has been approximately $1,500
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a. If you want to be 95% sure that you have estimated average family food expenditures within $100, how many families do you need to survey?
Since E = zs/sqrt(n)
n = [zs/E]^2
n = [1.96*1500/100]^2 = 865 when rounded up
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b. How many do you need to survey if you want to be 99% sure?
n = [2.5758*1500/100]^2 = 1493 when rounded up
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Cheers,
Stan H.

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