Fig. 2.

Results obtained by Morgan (32) when members of the Executive Committee of the EPA Science Advisory Board were asked to assign numerical probabilities to uncertainty words that had been proposed for use with EPA cancer guidelines (33). Note that even in this relatively small and expert group, the minimum probability associated with the word “likely” spans 4 orders of magnitude, the maximum probability associated with the word “not likely” spans more than 5 orders of magnitude, and there is an overlap of the probabilities the different experts associated with the two words.