Does MLwiN need repeated measures data to be in long or in wide format?
• I’m trying to set up a model using repeated measures data (with occasion within student within school). Looking at the example data, I see that level 1 ID has to be unique. Does this mean that the repeated measures have to be stored in the “wide” format? • No, MLwiN actually requires repeated measures data to be in the long, not the wide, format when it comes to analysis. The User’s Guide (chapter 13, section 13.2) shows how to convert data from wide to long format. However this does not mean that the level 1 IDs are no longer unique. In repeated measures analysis, occasion (time) is regarded as level 1, student (in your case) becomes level 2, and so on. Nor does it matter that the natural level 1 ID, Occasion Number, will have the same value for more than one row in the dataset since we do not have to use this as our level 1 ID but can create a new ID variable. A unique level 1 ID, which will give a different number to each occasion-person combination, can be created by selecting Ge
