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constructing a confidence interval around a sample variance

brew32

New member
Joined
Sep 27, 2009
Messages
7
Do not thoroughly understand, but this is what I came up with:

To construct a confidence interval around a mean or around a difference between two means, the basic formula is: (sample statistic) ± (test statistic)(standard error of sample statistic). The value of the test statistic (either a z or a t) is the same for both the + and the – side. This is not the case when constructing a confidence interval around a sample variance.
Why?

The confidence interval is not symmetric about the sample variance. This contrasts with confidence intervals for the distribution mean, which are always symmetric about the sample mean.
 
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