Show that for the problem of testing for the center of symmetry discussed in Sections 11.2 and 11.3, the efficacies of the t , sign, and Wilcoxon signedrank tests are given by 1/σ, 2f (0), and 2

√

3



f 2(z) dz, respectively, where

σ and f are the standard deviation and pdf of F, respectively.