Abstract
Let t i = X i/s, i = 1, 2 be noncentral Student t-variates with noncentrality parameters δi, where x 1, x 2 and s are independent. The simultaneous distribution of t 1 and t 2 is studied and the power function of the studentized maximum and minimum modulus tests are tabulated for significance level 0.05, degrees of freedom 1, 2, 5, 10, 20, 50, ∞ and δ1, δ2 =0(1)5. Asymptotically exact approximations to these power functions are discussed. The marginal power of the maximum modulus test is also tabulated.