Negative values
imply that people within a cluster (or PSU) are more different from each
other than they would have been had you sampled randomly (i.e., not by
cluster). Intuitively this makes no sense.
As the great diagnostician Charcot was fond of saying, '�a ne l'emp�che
pas d'exister'. There is one occasion on which this may indeed be true:
where the PSU is a group of people who form a team or social unit
characerised by a division of labour. A family, for example, or a
community mental health team, will combine people with different
specialisations and points of view. Two people randomly sampled from
within such a PSU will be more sharply differentiated than two people
sampled from the population.
