SOLUTION: Find the 95% confidence interval for the standard deviation of the lengths of pipes if a sample of 11 pipes has a standard deviation of 12 inches.

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Question 1040406: Find the 95% confidence interval for the standard deviation of the lengths of pipes if a sample of 11 pipes has a standard deviation of 12 inches.
Answer by robertb(5830) About Me  (Show Source):
You can put this solution on YOUR website!
[sqrt%28%28%28n-1%29s%5E2%29%2FX%5E2%5Balpha%2F2%5D%29,sqrt%28%28%28n-1%29s%5E2%29%2FX%5E2%5B1-alpha%2F2%5D%29 ]
=[sqrt%28%2810%2A12%5E2%29%2FX%5E2%5B0.025%5D%29,sqrt%28%2810%2A11%5E2%29%2FX%5E2%5B0.975%5D%29 ]
=[sqrt%281440%2F20.483%29,sqrt%281440%2F3.247%29 ]
= [8.38, 21.06]
where X%5E2%5Balpha%2F2%5D+ is the chi-square distribution with df 11-1 = 10 and alpha+=+0.05.