I have conducted a randomised controlled trial design (2 groups - experimental and control) with data collection at two time points (T1 and T2). I want to use the Multiple Imputation Method in SPSS to address item non-response (i.e. item-level missing data) at T1 and T2. It makes sense to me that MI will insert data points at T1 and T2 for questions that a participant has missed out. But it does not make sense to me that MI will insert data points at T2 for respondents who didn't even open up the second survey - they are systematic missing data at T2. If I allowed MI to do that then it would 'fill in' all the responses for the entire survey for some participants at T2. My datafile is set up in long format with each row as a participant and the T1 variables in columns and then the T2 variables in columns.
My questions: 1. Am I correct to think that MI should not insert data into T2 cells for participants who didn't do any of the questionnaire (i.e. systematic missing)? 2. If yes, how can I stop SPSS addressing those particular respondents? I can see how I can target different variables for MI but not different participants.
My question isn't really about the appropriateness of MI or my missing data. I'm ok up to the point of actually running the MI itself.
I'm using SPSS v224.
Thanks in advance,