What is a Scenario Parameter?

Scenario parameters are placeholders like variables, only they are used to represent a value that changes from scenario to scenario. For example, if you want to run three model scenarios experimenting with different numbers of resources, you would enter a scenario parameter Quantity field, and then define three different scenarios with three different numbers in the Scenarios tab of the Scenarios & Parameters dialog.

What is the real value of using scenario parameters as compared to making the changes directly to the model? Good question! Scenario parameters combined with scenarios allows the comparison of all experiments on the same output with no extra work on you part. Scenario parameters also allow the optimizer to automatically change values to find the best solution.

Scenario Parameters

New This button creates a new parameter that may then be edited. By default, all scenario parameters start with “p_.” The common prefix avoids naming conflicts with all other model entries and makes these names easy to identify.

Delete This button deletes the selected parameter.

Name The name of the parameter to be used in the model in place of actual values.

Default Value The value of the parameter when the Save & Simulate Chart menu item is selected rather than Run Scenarios.

Move Up Moves the selected parameter up in the list.

Move Down Moves the selected parameter down in the list.

How To – Define a scenario parameter

1. From the Simulation menu select Define Scenarios.

2. Click on the Scenario Parameters tab in the dialog (as shown on the previous page).

3. Click on the New button.

4. Enter the name of the parameter.

5. Enter a default initial value. This could be a specific number (e.g. number of resources) or a distribution function.

Using Scenario Parameters

To make use of the scenario parameters you have defined for your scenarios, you must enter the name of the parameter in place of the value it will represent in the model. For example, you may want to enter a different number of resources for each experiment. So you would enter the name of the parameter in the Quantity field on the General properties tab of that resource, as shown below.

What’s Changeable with a Scenario Parameter?

Any field, action logic, distribution, or statement normally occupied with a number could be replaced with a scenario parameter. Some examples include:

Scenario parameter entries to the activities dialog.

In the activities dialog, all capacities may include a scenario parameter. In addition, any distribution entry allows adjustment with a scenario parameter. However, notice that the name and object type don’t accept a scenario parameter.

Use a single scenario parameter to change many fields at the same time. For example, when changing the quantity of a resource, also change the capacity of every activity where they work. changing the capacity in this fashion avoids artificial limitations due to capacity.

Change the batch quantity using scenario parameters.
Changing the priority of a Get statement in Action Logic using scenario paramenters.

Change many other things using scenario parameters to replace values in a model.

Additional topics

What is a scenario?

How can I optimize scenario parameters?

What is Optimization?

How can I compare different models on the same output report?

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