describeratdata shows the following features: Number of unique school,
number of unique groups of raters/assessed, and for each group, the school
to which the group belongs, the group identifier, the ratings that are
actually used, the count of assessors, the count of assessed, the number of
missing ratings, the bias in the ratings, the number of ratings less than
the midrating, the number of ratings equal to the midrating, the number of
ratings larger than the midrating. Function describeratdata is useful for a
first check of the ratings./cr N.B. Unavailable values (NA) on the diagonal
are not counted as mssing ratings.