Question

We wish to create a 90% confidence interval for the Variance given that a sample of 30 has a standard deviation of 2. Find the Lower value for the confidence interval.Round to tenths.

Answer #1

Given that, sample size (n) = 30

sample standard deviation (s) = 2

confidence level = c = 0.90

=> significance level = 1 - c = 1 - 0.90 = 0.10

Degrees of freedom = n - 1 = 30 - 1 = 29

Using Excel we get, chi-square critical value as follows:

The 90% confidence interval for population variance is,

Where,

Upper value for the confidence interval is
**2.7**

Lower value for the confidence interval is
**6.6**

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A sample of 36 gives a proportion of 0.72. Find the lower value for
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Weights of men: 90% confidence; n = 14, = 161.5 lb, s =
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c. Confidence Interval given the sample standard deviation:
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e) Find the critical value:
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