# Are Cohen's d (effect size) and d prime from the signal detection theory measuring the same thing?

Are d prime (d') in signal detection theory and Cohen's d (mainly reported in the context of the general linear model) measures for the same thing (i.e., the difference of the means in SD-units), and just termed differently? Or is there any difference between those two measures?

• might as well add the z-score in there too. :) – John Jan 20 '12 at 17:56
• @John, there are similarities, but there is one important distinction: Cohen's d (etc.) is calculated from the relationship between 2 distributions, whereas z-scores are calculated within 1. – gung - Reinstate Monica Jan 21 '12 at 4:57

• +1 but this answer would improve if you include explicit formulas for Cohen's d and for d-prime. They both seem to be equal to $\mu_1-\mu_2$ divided by some measure of dispersion, it's just that they use slightly different measures of "pooled dispersion". – amoeba Sep 14 '16 at 14:21
• @amoeba, nope, that's the one. The "formal definition" they list first is assumed for the latent variables. Note that the "estimate of d'... is calculated as: $d' = Z(\text{hit rate}) − Z(\text{false alarm rate})$". No SDs are actually computed using either the population or sample formulas. – gung - Reinstate Monica Sep 14 '16 at 14:58