Creates a grouping variable which divides the sample in two groups (high and low scorers) of roughly equal size, without taking into account persons with extreme scores.
score_groups(dat.items, label = FALSE)A data frame with the responses to the items.
If TRUE the levels of the group factor are named according to the split used, if FALSE (default) the group factor has levels 1 and 2.
Score group variable, a factor with two levels.
The score groups are used for tests of item homogeneity.