The comparison of designs for sequential clinical trials with covariate information

The paper develops methods for the comparison of randomized rules of the biased coin type for the sequential allocation of treatments in a clinical trial. One important characteristic is the loss, which measures the increase in the variance of parameter estimates due to the imbalance caused by randomization. The other important characteristic is the selection bias measuring the probability of correctly guessing which treatment is to be allocated next. The combination of these two measures leads to the elucidation of admissible designs. Simulations provide clear plots of the behaviour of the designs and make it possible to distinguish good designs from those which are less good.