Bounded distribution

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Bounded distribution

You can create bounded distributions to avoid undesired behavior when samples come from the ends of a distribution tail. For example, you might specify demand that has a normal distribution with mean of 5 and standard deviation of 2. In this case, some samples from the distribution will be negative and will result in nonsensical values and potentially instability in the model.

In these situations, you can specify a lower and upper bound as optional parameters to the distribution that will act as bounds. The bounded distributions and parameters are:

Distribution	Parameters
Bounded Normal (BN)	Mean Std Dev Min (default = 0) Max (default = INF)
Bounded Exponential (BE)	Mean Max (default = INF)
Bounded Lognormal (BL)	Mean Std Dev Min (default = 0) Max (default = INF)

When you apply bounds to the distribution, the graph reflects these parameters:

In the event of a sample that is outside the bounds, the min or max of the bounded distribution is used. With many samples, this results in a slight change to the population mean and standard deviation (in case of a normal distribution). From a statistical standpoint, resampling is not recommended. You could get a sample of -0.01, then resample to get a value that was at the other end of the distribution.

The new distributions and parameters for bounded distributions are available on all columns that support distributions:

Table	Column
Production Policies	Fixed Order Time Unit Production Time Fixed Order Cost Unit Production Cost
Site Sourcing Policies Customer Sourcing Policies	Fixed Order Cost Unit Sourcing Cost Fixed Order Time Source Lead Time Unit Sourcing Time
Transportation Policies	Shipment Period Variable Transportation Cost Return Trip Time Load Time Unload Time Load Unit Time Unload Unit Time CO2
Production	Quantity Time Between Orders Order Time Due Date Occurrences
Process Steps	Unit Process Time Fixed Order Process Time Average Changeover Time
Customer Demand	Quantity Due Date Order Time Occurrences Time Between Orders
Shipments	Quantity Order Time Due Date Occurrences Time Between Shipments
Shipment Routes	Time
Work Center Changeovers	Time

Last modified: Wednesday May 15, 2024

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