Returns the righttailed probability of the chisquared distribution. The χ2 distribution is associated with a χ2 test. Use the χ2 test to compare observed and expected values. For example, a genetic experiment might hypothesize that the next generation of plants will exhibit a certain set of colors. By comparing the observed results with the expected ones, you can decide whether your original hypothesis is valid.
Important: This function has been replaced with one or more new functions that may provide improved accuracy and whose names better reflect their usage. Although this function is still available for backward compatibility, you should consider using the new functions from now on, because this function may not be available in future versions of Excel.
For more information about the new functions, see CHISQ.DIST function and CHISQ.DIST.RT function.
Syntax
CHIDIST(x,deg_freedom)
The CHIDIST function syntax has the following arguments:

X Required. The value at which you want to evaluate the distribution.

Deg_freedom Required. The number of degrees of freedom.
Remarks

If either argument is nonnumeric, CHIDIST returns the #VALUE! error value.

If x is negative, CHIDIST returns the #NUM! error value.

If deg_freedom is not an integer, it is truncated.

If deg_freedom < 1 or deg_freedom > 10^10, CHIDIST returns the #NUM! error value.

CHIDIST is calculated as CHIDIST = P(X>x), where X is a χ2 random variable.
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.