Statistics variance
2015-03-19 7:54 am
Suppose that you want to construct 95% confidence interval for the average amount spend on books by student in their first year at university. Assume that the amount spent is normally distributed with mean μ and variance σ^2 . The interval is to have a margin of error of $2. You estimate will be based on a sample size of 625. What is the variance of the amount spent on books by each student?
回答 (1)
2015-03-20 10:54 am
✔ 最佳答案
Margin of error for a 95% confidence interval based on normal population is1.96 σ / √n where σ is the s.d. of the normal population and n is the sample size.
Therefore,
1.96 σ / √625 = 2
1.96 σ / 25 = 2
1.96 σ = 50
σ = 50/1.96
σ² = (50/1.96)²
σ² = 650.7705123 is the required variance.
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