Sir R. A. Fisher, a famous statistician, showed that the critical values of a chi-square distribution can be approximated by the standard normal distribution
where v is the degrees of freedom and z Subscript k is the z-score such that the area under the standard normal curve to the right of z Subscript k is k. Use Fisher's approximation to find χ2 0.995 and χ2 0.005 with 90 degrees of freedom. Compare the results with those found in the table of the chi-square distribution.
