In Excel 2010, the CHIDIST() function was replaced with the CHISQ.DIST.RT() function, and the CHISQ.DIST() function was added to increase the accuracy of the results. To ensure the backward compatibility of CHISQ.DIST.RT(), the CHIDIST() function is still available.
Definition. This function returns the values of the right-tailed probability of chi-square distribution. The χ2 c2-distribution is required for a c2-test. Use this test to compare observed and expected values. For example, an experiment might hypothesize that the regular use of vitamins reduces the risk of colds. By comparing the observed results with the expected results, you can validate this hypothesis.