d'

The sensitivity index or d' (pronounced 'dee-prime') is a statistic used in signal detection theory. It provides the separation between the means of the signal and the noise distributions, in units of the standard deviation of the noise distribution.

An estimate of d' can be found from measurements of the hit rate and false-alarm rate. It is calculated as:

d' = Z(hit rate) - Z(false alarm rate),

where function Z(p), p ∈ [0,1], is the inverse of the cumulative Gaussian distribution.

A higher d' indicates that the signal can be more readily detected.

See also

• Receiver Operating Characteristic (R.O.C.)
• Summary Statistics

References

• Wickens, Thomas D. (2001) Elementary Signal Detection Theory, OUP USA. ISBN 0195092503 (Ch.2, p.20). Excerpts

External links

• Interactive signal detection theory tutorial including calculation of d'.