# Finding the mean and the sample size

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A bank wants to estimate the mean dollars that each credit card holder will spend each month. It would like to be within + or - $10 of the true mean with a 98% condfidence level. The standard deviation is $500. How many card holders should be sampled?

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A bank wants to estimate the mean dollars that each credit card holder will spend each month. It would like to be within + or - $10 of the true mean with a 98% condfidence level. The standard deviation is $500. How many card holders should be sampled?

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Since the population standard deviation is known, we use z value for calculation.

The two-tailed 98% z value is z = 2.33

Let N = sample size

The confidence interval ...

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