Fig. 3

Distribution functions under various prior assumptions. The flat prior assigns equal (low) probability for each unfavourable outcome proportion from 0 % to 100 %. The sceptical prior assigns a higher probability to a 20 % proportion of unfavourable outcomes (a regimen that would not be suitable for evaluation in a phase III trial), and a lower probability to very high or very low proportions of unfavourable outcomes. The enthusiastic prior assigns a high probability to proportions of unfavourable outcomes less than 10 % and lower probabilities to proportions greater than 10 %. The sceptical prior has a median at 26.4 % and the enthusiastic prior has a median at 3.3 %