CHIINV(p,dof)
CHIINV function returns the inverse of the one-tailed probability of the chi-squared distribution.
If @p < 0 or @p > 1 or @dof < 1 CHIINV returns #NUM! error.
This function is Excel compatible.
CHIINV(0.98,7) equals 1.564293004.
CHIDIST, CHITEST.