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Sample size from a survey of food costs per year

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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?

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The solution provides step by step method for the calculation of sample size. Formula for the calculation and Interpretations of the results are also included.

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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, ...

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