Answer:
Confidence interval variance [21.297 ; 64.493]
Confidence interval standard deviation;
4.615, 8.031
Step-by-step explanation:
Given :
Variance, s² = 34.34
Standard deviation, s = 5.86
Sample size, n = 27
Degree of freedom, df = 27 - 1 = 26
Using the relation for the confidence interval :
[s²(n - 1) / X²α/2, n-1] ; [s²(n - 1) / X²1-α/2, n-1]
From the chi distribition table :
X²α/2, n-1 = 41.923 ; X²1-α/2, n-1 = 13.844
Hence,
[34.34*26 / 41.923] ; [34.34*26 / 13.844]
[21.297 ; 64.493]
The 95% confidence interval for the population variance is :
21.297 < σ² < 64.493
Standard deviation is the square root of variance, hence,
The 95% confidence interval for the population standard deviation is :
4.615 < σ < 8.031
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