CHISQ.INV.RT function
Returns the inverse of the righttailed probability of the chisquared distribution.
If probability = CHISQ.DIST.RT(x,...), then CHISQ.INV.RT(probability,...) = x. Use this function to compare observed results with expected ones in order to decide whether your original hypothesis is valid.
Syntax
CHISQ.INV.RT(probability,deg_freedom)
The CHISQ.INV.RT function syntax has the following arguments:

Probability Required. A probability associated with the chisquared distribution.

Deg_freedom Required. The number of degrees of freedom.
Remarks

If either argument is nonnumeric, CHISQ.INV.RT returns the #VALUE! error value.

If probability < 0 or probability > 1, CHISQ.INV.RT returns the #NUM! error value.

If deg_freedom is not an integer, it is truncated.

If deg_freedom < 1, CHISQ.INV.RT returns the #NUM! error value.
Given a value for probability, CHISQ.INV.RT seeks that value x such that CHISQ.DIST.RT(x, deg_freedom) = probability. Thus, precision of CHISQ.INV.RT depends on precision of CHISQ.DIST.RT. CHISQ.INV.RT uses an iterative search technique. If the search has not converged after 64 iterations, the function returns the #N/A error value.
Example
Copy the example data in the following table, and paste it in cell A1 of a new Excel worksheet. For formulas to show results, select them, press F2, and then press Enter. If you need to, you can adjust the column widths to see all the data.