Chi2DistriIntegral
Declaration: 
Chi2DistriIntegral (chi2: double; df: integer): double; 
The function Chi2DistriIntegral returns the probability p for a given critical value chi2 , and a given number of degrees of freedom df . The probability p is equal to the integral of the chisquaredistribution between zero and the value of the parameter Chi2 . The returned value may vary between 0.0 and 1.0.

Hint 1: 
The calculated value is exact to about 8 decimal places. 
Hint 2: 
The function Chi2DistriIntegral calculates the integral from 0.0 to the ChiSquare value. This differs from the convention of how the integral of the ChiSquare distribution is used in many statistical packages, which tabulate the integral between +infinite and the ChiSquare value. Thus you have to use 1Chi2DistriIntegral to get comparable results. For example, in order to calculate the function CHIDIST(x,df) of Microsofts Excel® you have to use 1Chi2DistriIntegral(x,df). 
