Figure 1.

Power comparisons are a function of alpha level. By definition q = (δ_b − δ_a)/δ_a is the relative increase in the NCP purchased by the additional degrees of freedom. Note the log scale on the x-axis of all four graphs. (a,b) For different values of α, power (p) of T_a, and degrees of freedom, we show how large q must be for T_b and Ta to have equal power. (c,d) For different values of q and α and with the power of T_a fixed at 65% we show the percentage of power gained by using T_b (i.e., 100% × [$[1-F_{{\nu }_b(1+q)\Delta (\alpha ,0.65,{\nu }_a)}(F_{{\nu }_b,0}^{-1}(1-\alpha ))-0.65]$/0.65).