The data set contains 10 groups, each group has 30 observations. The format is list, where there are four elements:
x: the level 1 continuous predictor.
y: the level 1 continuous outcome.
m: the matrix of mediators, where there are one level 2 mediator, m.1, and two level 1 mediators, m.3 and m.4. m.4 is categorical with 3 levels.
level: the group level for each observation.