SOLUTION: You want to obtain a sample to estimate a population mean. Based on previous evidence, you believe the population standard deviation is approximately σ = 30.8 . You would l

Question 1183098: You want to obtain a sample to estimate a population mean. Based on previous evidence, you believe the population standard deviation is approximately
σ
=
30.8
. You would like to be 95% confident that your estimate is within 1.5 of the true population mean. How large of sample size is required
Answer by math_tutor2020(3817) (Show Source): You can put this solution on YOUR website!

sigma = 30.8

At 95% confidence, the critical z value is roughly z = 1.960 (use a table or calculator to find this).

The error we want to have is E = 1.5

Now we can compute the min sample size needed
n = (z*sigma/E)^2
n = (1.960*30.8/1.5)^2
n = 1619.68685511111
n = 1620
Always round up to ensure we clear the hurdle.

Answer: 1620

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