PSY 3108 Lecture Notes - Lecture 2: Dorsal Root Ganglion, Detection Theory, Mechanoreceptor
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Sensitivity is measured by the proportion of hits (ph= nhits/ ntesttrials) and proportions of false alarms (pfa= nfa/ ncatch) basic sensitivity = ph- pfa what we actually calculate, however, is d"= z(ph)- z(pfa) Note that z(pfa) means function z, not multiply by z. For z scores of 1 and 0 we would get positive and negative infinity, so instead we use. 0 is usual minimum and 4. 66 is conventional max. The lower the c, the more a person"s tendency to say yes . Isosensitivity curves- a range of ph and pfa can produce the same values. This occurs when sensitivity remains the same, but criterion shifts. Many reasons, for example the payoff matrix (i. e. cost for false alarm) Signal detection theory- any attempt at detecting a signal has to contend with competing noise. Noise can be actual noise or even neuron chatter etc. (from detector)