I have written a DES model to simulate canal traffic passing through a
flight of 6 locks. The system consists of two-way traffic(customers), with
bi-directional locks (servers).
In the model random numbers for the service procedure are generated using
the inverse transformation method, to create 'a day in the life' of the lock
system. I inititally modelled the lock procedure(service) using the Normal
distribution, as it fits this distribution. However on occasions, due to
high variance, there is a small chance that negative values can be produced.
This is clearly not acceptable as it cannot take minus 0.5 minutes for a
boat to enter a lock. In view of constraint I have now chosen Log-Normal
because it is closely related to the Normal distribution, but is also is a
positive and positively skewed distribution.
Has anyone else used a Log-Normal distribution to describe length of service
in a simulation model. Can anyone offer more information on this
distribution as there appears to be very little written about it, compared
to the Normal.
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