CHIINV function
Description
Returns the reverse of Chi-squared distribution.
CHIINV(P,df) returns the Chi-squared value corresponding with the one-tailed probability P (P-value) and the specified degrees of freedom df.
CHIINV is the inverse function of the CHIDIST function.
The argument P can be a real number or a matrix. When it is a matrix, the function returns a matrix with the same dimensions and with the CHIINV function applied to all elements.