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I have a question here that asks me to find how large a sample size is, but I have no Standard deviation. How would you tackle this>

How large a sample size do we need to estimate the mean annual income of natives in New York, correct to within $1000 with probability 0.99? No information is available to us about the standard deviation of their annual income. We guess that nearly all of the incomes fall between $0 and $120,000 and that this distribution is approximately normal.

Here's what I see:

1 - alpha = 0.99 therefore alpha =0.01 /2 = 0.005

This gives a Z* of 2.575 (because it states normal distribution)

The 99% CI is (0, 120000).

I know that n = [Z*s/m]squared, buty I have neither s, nor m....

As always, the feedback and guidance is appreciated =)

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# Sample size without standard Deviation

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