THE POWER OF RANDOMIZATION TESTS FOR SINGLE-CASE PHASE DESIGNS

Monte Carlo methods were used to estimate the power of randomization t ests used with single-case designs involving the random assigmment of treatments to phases. The design studied involved 2 treatments and 6 p hases. The power was studied for 6 standardized effect sizes (0,.2,.5, .8, 1.1, and 1.4), 4 levels of autocorrelation (Ist order autocorrelat ion coefficients of -.3, 0,.3, and .6), and 5 different phase lengths (4, 5, 6, 7, and 8 observations). power was estimated for each conditi on by simulating 10,000 experiments. The results showed an adequate le vel of power (>.80) when effect sizes were large (1.1 and 1.4), phase lengths exceeded 5, and autocorrelation was not negative.