I have an eye tracking study in which two groups of subjects (patient and control) are completing a face recognition task in which they learn a set of faces and then are shown faces one at a time and have to decide if each face is one that they learned earlier. During the task, we are recording their eye movement patterns to see if they look more to the top half or bottom half of the face on learning faces in the learning phase, target faces in the test phase, and distractor faces in the test phase. Thus, we have calculated the average duration of looking time to each region of interest (upper face v lower face) for each type of face (learning v target v distractor).
In one analysis we are examining the control group only. Thus, we are conducting a 2 (face half: upper v lower) x 3 (face type: learning v target v distractor) repeated measures ANOVA.
We have been told that we should always include subject as a random effect. My understanding is that, in SPSS terms, this means we would need to use SPSS MIXED. What I don't understand is WHY we should include subject as a random effect and how we would go about doing so. Should subject be included as a random effect by default simply because it is a repeated measures design?
I did find this, which seems to be on the topic. But I am having a hard time connecting the instructions here with what I am supposed to do with this particular data set. http://www.spss.ch/upload/1126184451_Linear Mixed Effects Modeling in SPSS.pdf
Thank you in advance for your help!
In one analysis we are examining the control group only. Thus, we are conducting a 2 (face half: upper v lower) x 3 (face type: learning v target v distractor) repeated measures ANOVA.
We have been told that we should always include subject as a random effect. My understanding is that, in SPSS terms, this means we would need to use SPSS MIXED. What I don't understand is WHY we should include subject as a random effect and how we would go about doing so. Should subject be included as a random effect by default simply because it is a repeated measures design?
I did find this, which seems to be on the topic. But I am having a hard time connecting the instructions here with what I am supposed to do with this particular data set. http://www.spss.ch/upload/1126184451_Linear Mixed Effects Modeling in SPSS.pdf
Thank you in advance for your help!