Equivalent Tests A x2 test involving a 2 * 2 table is equivalent to the test for the difference between two proportions, as described in Section 9-1. Using the claim and table in Exercise 5 “Splint or Surgery?” verify that the x2 test statistic and the z test statistic (found from the test of equality of two proportions) are related as follows: z2 = x2. Also show that the critical values have that same relationship.