> The covariate called Accuracy is actually a binary number when considering the trial data: 1 = correct and 0 = incorrect.
> In that case, would you proceed the same way to subtract the group mean for each condition of interest (i.e. Time1, Time2,
> Time3, and Time4)? For example, if the average accuracy for Time 1 across all participants is 88.7% correct, then would
> I subtract 88.7 from a 1 or a 0, depending whether the trial was correct or incorrect, respectively. Something seems weird
> about this approach with a binary variable.
How would you like to interpret your group analysis results with regard to Accuracy: associated with 1) the correct trials, 2) incorrect trials, or 3) some sort of average between correct and incorrect trials?
For 1) (and 2)), it's better to just separate those trials into two separate regressors, one for correct and the other for incorrect ones. For 3), one possibility (not as weird as your example) is to code them with 1 and -1, respectively, and set the mean to 0.
Gang