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## 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?