Question

A random sample of n = 11 observations was selected from a normal population. The sample mean and variance were x = 3.93 and s2 = 0.3216. Find a 90% confidence interval for the population variance σ2. (Round your answers to three decimal places.)

Answer #1

Chi-square critical values at 0.10 significance level with 10 df = 3.940 , 18.307

90% confidence interval for ^{2}is

(n-1) S^{2} / /2
< ^{2}<
(n-1) S^{2} / 1-/2

(11-1) * 0.3216 / 18.307 < ^{2}<
(11-1) * 0.3216 / 3.940

0.176 < ^{2}<
0.816

90% CI is **(0.176 , 0.816)**

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