# Confidence interval on Standard deviation

• I

## Main Question or Discussion Point

I read that confidence interval on standard deviation can be found using chi-square distribution. If I have a sample size N=500, and sample standard deviation= 3 with mean=0, and I need a 95% confidence, I wasn't sure what to set for degrees of freedom in chi-square formula. Is the degrees of freedom same as the sample size? Is there an online-tool that can do the math for you if I enter the values?

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.Scott
Homework Helper
You can calculate your confidence interval with this tool:
Confidence Interval

The degrees of freedom is you sample size minus one (499), but that is not required by this tool.

• iVenky
Hi,

Thanks for the reply, but I am interested in confidence interval of the standard deviation rather than the mean. The link that you mentioned doesn't contain the confidence interval for standard deviation

.Scott
Homework Helper
• iVenky
Thank you very much!