Hi. I have data on 600 participants at 5 time points with 2 measurements at each time point for average (some missing data). I want to look at the change in nutrient intakes over the 5 time points. I have the data in long format. I want to include a random effect at the participant level, but I'm unsure how to do this using the mixed command - do I use participant ID in the random effect equation? Any help much appreciated.