Hi, I haven't took statistics for a few years and I'm trying to help out a friend. Heres the question.
She wants to be 95% confident that her estimate is correct. if the standard deviateion is $1050, how large a sample is needed to be accurate within $200.
How would you solve this? Thanks!
How to solve this statistics problem?
The formula for sample size in this case is
n = (Z^2)(standard deviation^2)/error^2
where Z is the Z value corresponding to the desired confidence level
In this case it would be (1.96^2)(1050)^2/(200^2) = 105.88 which you would round up to 106.
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