In each HRG there is always a small number of cases
which are characterized by the excessively long length of
stay in the hospital. In this situation, the cost of excess bed
days beyond the upper trim-point (the upper quartile of the
length of stay distribution for that HRG plus 1.5 times the
interquartile range) are excluded from calculation of average
HRG costs and calculated separately [6]. Similar procedure
is also applied for patients treated ambulatory as well as
during single day treatments. The formula for unit cost of
HRG in each setting (cij) is: