Originally my script did not include the automatic calculation of D, but after realizing I could do this, I used a template to add that feature.
Unfortunately now I'm stuck with about 50 subjects for whom I do not have a D. I've tried to figure out which formula was used in the newer ones that are calculated by recomputing the score using Greenwald's D formula and comparing it to the output. So far I cannot get the same Ds from my data that Inquisit is producing. Could someone tell me what formula is used in the automatic calculation of D? I just want to make sure I'm going through the same process for my initial 50 data points.
Thanks,Erica
It's the improved scoring algorithm put forth in Greenwald et al. (2003). Also see https://www.millisecond.com/forums/Topic3444.aspx.
Thanks Dave,
That is the formula I'm using. It produces D scores that are close, but not the same as the ones automatically generated. Attached is an excel spreadsheet where I replicate the computation for two examples (one producing negative Ds instead of positive ones). Am I missing something?
Erica
Erica: Minor differences may be due to rounding error. Also, in case you're using Excel to do the actual calculations, note that many of Excel's statistical functions use notoriously bad / inaccurate algorithms (e.g. McCullough, 2005, 2008; Yalta, 2008; ). In case of the reversed sign, you have to take block order into account. I recommend you work through the various SPSS syntax procedures available for calculating D from the raw latency data.