A New Approximation for the Chi-Square Integral
H. L. Gray, R. W. Thompson, G. V. McWilliams · Mathematics of Computation · 1969
In this paper a new method for estimating the value of an improper integral by a finite sum is introduced. In particular, the method is applied to the Chi-Square integral and proves to be of some value in estimating the value of this integral for values equal or greater than .9.