29. In the 2 X 2 table for matched pairs, in the notation of Section 9, the correlation between the responses of the two members of a pair is For any given values of 'lT1 < 'lT2, the power of the one-sided McNemar test of H :'IT\ = 'lT2 is an increasing function of p. [The conditional power of the test given X + Y =

d, X = x is an increasing function p = POi/(POI + PIO)') Note. The correlation p increases with the effectiveness of the matching, and McNemar's test under

(b) of Problem 28 soon becomes more powerful than Fisher's test under (a). For detailed numerical comparisons see Wacholder and Weinberg (1982) and the references given there.