ABSTRACT
Associative evidence is sometimes accompanied by statistical testimony about the incidence rate of the “matching” characteristic. In a criminal trial, the percentage of defendants in some relevant comparison population who are guilty is a base rate statistic, while the percentage of some relevant population who possess a characteristic linking the defendant to the crime is an incidence rate statistic. The conflict stems largely from differing assumptions about the way jurors respond to incidence rate statistics. The number of subjects, who were apparent victims of the fallacies, and mean judgments of guilt, were significantly affected by a subtle manipulation in the way incidence rate statistics were presented. The legal debate over the admissibility of incidence rate statistics in connection with associative evidence stems largely from differing assumptions about the way jurors are likely to respond to evidence. The findings of the present research cast some initial light on this issue.
