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categories. The dependent variable in this study is the occupant injury severity, which is
classified into two categories in this research: severe injury and minor injury.
{ (5.5)
If we assume that:
{ (5.6)
Then the probability of road user n suffering a severe injury is given by:
( )
( ( )
( ) (5.7)
where, F is the cumulative density function of
If we assume that has a Burr-10 distribution, then we have the skewed logistic or Scobit
model (Nagler, 1994):
( ) (5.8)
)
(
where,
Note that if , then the Burr-10 distribution is equivalent to the logistic distribution and
the scobit model is reduced to the standard binary logistic model. Hence, the additional scale
parameter, serves as a measure of skewness (Nagler, 1994).
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