dprime.mAFC {psyphy}

d' for m-alternative Forced-choice

Description

Calculate the value of d' for an m-alternative forced choice paradigm

Usage

dprime.mAFC(Pc, m)

Arguments

Pc

The proportion of correct responses based on either the Hit rate or based on an unbiased observer

m

The number of alternative choices, an integer > 1.

Details

The probability of a correct response in m-alternative forced-choice, assuming independence, is based on the product of the likelihoods of the signal alternative generating the strongest response and the m - 1 noise alternatives generating responses less than this value (Green and Dai, 1991). For a Yes-No paradigm, the sensitivity is calculated more simply as

d' = \code{qnorm}(H) - \code{qnorm}(F)

where H and F are the Hit and False Alarm rates, respectively.

Value

Returns the value of d'

Note

Currently is only valid for d' in the interval [-10, 10] which should be well outside the range of sensory differences that this paradigm is used to investigate.

Author(s)

Kenneth Knoblauch

References

Green, D. M. and Dai, H. (1991) Probability of being correct with 1 of M orthogonal signals. Perception & Psychophysics, 49, 100–101.

Green, D. M. and Swets, J. A. (1966) Signal Detection Theory and Psychophysics Robert E. Krieger Publishing Company

See Also

See Also dprime.ABX, dprime.SD, dprime.oddity

Examples

dprime.mAFC(0.8, 4)