Dprimes and Betas may be computed in SPSS using the probit function. For four columns of input: Hits (HI), FN (False Negatives), FP (False Positives), CN (Correct Negatives) [CUT AND PASTE SYNTAX IN BOX BELOW INTO SPSS SYNTAX WINDOW]
* Computes Dprimes and Betas for signal detection theory * amend data input as required SET FORMAT F10.5. DATA LIST FREE / HI FN FP CN. BEGIN DATA 9 1 3 7 6 4 2 8 END DATA. IF (HI EQ 0) HI = 0.5. IF (FN EQ 0) FN =0.5. IF (FP EQ 0) FP = 0.5. IF (CN EQ 0) CN =0.5. COMPUTE HIP = HI / (HI + FN). COMPUTE FPP = FP / (FP + CN). COMPUTE DP = PROBIT(HIP) - PROBIT(FPP). COMPUTE BETA = EXP(-0.5*(PROBIT(HIP)**(2))) / EXP(-0.5*(PROBIT(FPP)**(2))). LIST VARIABLES= DP BETA HI FN FP CN.
Excel syntax available at http://psych.utoronto.ca/~creelman/