A Appendix

To quote Armitage [1993], "the classical theory of experimental design deals predominantly with A. Fisher, worked in agricultural research, where the outcome of a field trial is not available until Consider these problems first from the perspective of hypothesis testing . Perform the test too early, and the Type II error probability will be high, resulting in many small effects being undetected. For instance, consider one-sided "no-harm" testing applications where the goal is to detect (possibly To address this concern, the experimenter might wish to estimate the effect by computing a confidence interval. The experimenter cannot hope to "monitor" the effect of each arm by computing multiple fixed-n Instead of stopping the experiment at a predetermined sample size, it is more natural and useful for the stopping rule to be data-dependent in sequential applications. That is, to perform optional continuation .