Gang,
I also wanted to mention that two of my participants do not have accuracy data, so I am reluctant to analyze correct and incorrect trials separately because I will not be able to include them in the analysis.
So, would it be best to handle the continuous nuisance variables (confidence and response time) at the trial level using amplitude modulated regressors and then handle the binary nuisance variable (accuracy) at the group level using 3dLME? Note that accuracy becomes a continuous measure when it is calculated for each condition of interest (e.g., Time1= 90% correct, Time2= 80% correct, Time3 = 70% correct and Time4=60% correct).
Or should I simply use 3dLME to handle all of the nuisance variables and forget the amplitude-modulated approach?
Best,
Christine