[visionlist] How to compute d' when hit rate or false alarm rate is 0 or 1?

[Hang Zhang]

Hi,

In signal detection theory, sensitivity d' is computed as the z-score difference between false alarm rate and hit rate. I am puzzled about what is the z-score for a 0 or 1 rate, because theorically the value is indefinite. But an indefinite d' for an observer in a psychological experiment seems unreasonable... Could someone tell me how to compute d' when hit rate or false alarm rate is 0 or 1? Many Thanks. 

Best,		
Hang

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Hang ZHANG, PhD Candidate
State Key Laboratory of Brain and Cognitive Science
Institute of Psychology, Chinese Academy of Sciences
4A, Datun Road, Chaoyang District
Beijing 100101, China
Tel: 8610 6483 7209
Fax: 8610 6487 2070
Email: zhangh at psych.ac.cn
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