Abstract: In order to find out a and f(u) (average degree of believing), the method of Set-Valued Statistics in Fuzzy Sets can be directly introduced into the evalution method of the signal detectability theory to deal with the data collected from the experiment. This experiment proves that: a and f(u) is an index of recognition ability as good as d' and its meaning is even clearer; the calculation principles of a and f(u) do not require the normal distribution of original data, and repetitions of the experiment can be greatly reduced; the per- person-time judgement in the evaluation method is an experiment of Set- Valued Statistics.

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