Hey blind527.

Recall the chi-square distribution where (n-1)s^2/sigma^2 has a chi-square distribution with n-1 degrees of freedom. You are given sigma^2 as 6600^2 so you can look at the distribution for s^2 by using the appropriate chi-square PDF.

Usually in statistical inference, we do the opposite: we start with s^2 and try to make inferences on sigma^2 but we can do the same thing in reverse and it is in some cases very useful to do the unconventional thing.