# Math Help - Find Confidence

1. ## Find Confidence

Can someone please give me the final equation for confidence interval for variance when population mean is known.

I only need the equation. Thank you.

2. are you assuming normality?
If so, you pivot on

${\sum_{i=1}^n(X_i-\mu)^2\over \sigma^2}\sim\chi^2_n$

${\sum_{i=1}^n(X_i-\bar X)^2\over \sigma^2}\sim\chi^2_{n-1}$

3. Originally Posted by ilikec
Can someone please give me the final equation for confidence interval for variance when population mean is known.

I only need the equation. Thank you.
It is not difficult to find things using Google: http://www.stat.purdue.edu/~tlzhang/...chapter7_4.pdf

How to use Google should be taught at all institutes.

4. If you know MOO, then you use

$\sum(X_i-\mu)^2$ instead of $\sum(X_i-\bar X)^2$ and you use n degrees of freedom instead of n-1.