Definition of CHIINV
Returns the inverse of the right-tailed probability of the chi-squared distribution. If probability = CHIDIST(x,...), then CHIINV(probability,...) = x. Use this function to compare observed results with expected ones in order to decide whether your original hypothesis is valid.
The CHIINV function syntax has the following arguments:
Probability Required. A probability associated with the chi-squared distribution.
Deg_freedom Required. The number of degrees of freedom.
If either argument is nonnumeric, CHIINV returns the #VALUE! error value.
If probability < 0 or probability > 1, CHIINV returns the #NUM! error value.
If deg_freedom is not an integer, it is truncated.
If deg_freedom < 1, CHIINV returns the #NUM! error value.
Given a value for probability, CHIINV seeks that value x such that CHIDIST(x, deg_freedom) = probability. Thus, precision of CHIINV depends on precision of CHIDIST. CHIINV uses an iterative search technique. If the search has not converged after 100 iterations, the function returns the #N/A error value.