To estimate a population variance a Chi-Squared distribution is used,
• Chi-Squared: X2=σ2(n−1)s2 n: sample size s: sample standard deviation σ: population standard deviation (n−1): is also called “degrees of freedom”
• Chi-Square table gives critical value area to the right
The Confidence interval for the variance is given by:
• XR2(n−1)s2 < σ2 < XL2(n−1)s2
Determining Degrees of Freedom
How many degrees of freedom does a sample of size,
Determining the Critical Value for a Chi-Square Distribution (XR2 and XL2)
If a Chi-Squared distribution has 8 degrees of freedom find XR2 and XL2, with a
Chi-Squared confidence intervals
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