Question

Use the given degree of confidence and sample data to find a confidence interval for the population standard deviation σ. Assume that the population has a normal distribution. Round the confidence interval limits to the same number of decimal places as the sample standard deviation.

Weights of men: 90% confidence; n = 14, xbar = 156.9 lbs, s = 11.1 lb

A) 8.5lbs < σ < 16.5 B) 8.2lbs < σ < 15.6 lbs C) 8.7lbs < σ < 14.3lbs D) 9.0 < σ < 2.7lbs

Answer 1

Chi square critical values at 0.10 significance level with 13 df = 5.892 , 22.362

90% confidence interval for is

Sqrt [ (n-1) S2 / U ] < < Sqrt [ (n-1) S2 / L ]

sqrt [ 13 * 11.12 / 22.362 ] < < sqrt [ 13 * 11.12 5.892 ]

8.5 < < 16.5