Sample size calculation is based on the assumption that treatment with Ziprasidone will show an effect size of ES=1 compared to treatment with placebo. In order to demonstrate this difference at a significance level of 5% and a power of 80%, 17 patients per group are required, and a drop-out rate of approximately 8 patients per group (with no data available to be analyzed according to the intention-to-treat principle) must be accounted for.