Experiments

Figure 5.13 shows a sample Experiment window. The table in this window is sometimes referred to as the design matrix for an experiment. All the information that is associated with an experiment is displayed in the design matrix. Each row in the matrix is called a design point, and it contains values for a label, execution controls, factor settings, and responses measured during model execution.

You can add or remove design points by using the pop-up menu that opens when you right-click in the Experiment window. You can also use the pop-up menu to duplicate an existing design point. Select the design point in the Experiment window, and then right-click to open the pop-up menu. Select Replicate Design Point; a copy of the design point is added at the bottom of the design matrix.

Figure 5.13: Sample Experiment Window

The design matrix initially has four default columns, labeled PointName, StartTime, EndTime, and Replicates. The PointName column assigns a label to the design point. Although a default value (pointN) is generated for this field when you create the design point, you can edit this field to be any text you choose. The StartTime and EndTime values control the execution start time and end time (on the simulation clock) for an individual simulation run. The simulation clock begins running at time displayed in the StartTime field for the design point, and the simulation ends when the simulation clock reaches the time entered in the EndTime field. (Note that time has no unit in Simulation Studio.) The final default column in the design matrix, Replicates, contains a value that represents how many times you want to run this particular design point.

You can edit the default values for StartTime, EndTime, and Replicates by selecting Properties from the Experiment window pop-up menu and modifying the values in the Experiment Properties dialog box. The default values in the Experiment Properties dialog box are applied to new design points that are subsequently added to the Experiment window. Changes to the default values for StartTime, EndTime, and Replicates are not applied to existing design points.

Figure 5.14: Experiment Properties Dialog Box

Each of the StartTime, EndTime, and Replicates columns has a pop-up menu (which opens when you right-click the column name) that has a menu item called Set Value. You can use Set Value to change default values for new and existing design points. For example, Figure 5.15 shows the Set Value: Replicates dialog box, which you open by right-clicking the Replicates column name and selecting Set Value. The New Value text box enables you to specify a value for the number of replications. The All and Selected options enable you to specify whether the new value should be applied to all design points or to only the selected ones. The value that initially appears in the New Value field is the default replicates value, which is set in the Experiment Properties dialog box. The Set Value: EndTime and Set Value: StartTime dialog boxes have functionality similar to that of the Set Value: Replicates dialog box.

Figure 5.15: Set Value: Replicates Dialog Box

Only the default columns in the design matrix are necessary for you to actually run a simulation model. Figure 5.13 shows a design matrix with one factor, maxentities, and one response, Number Serviced. You can add any factors or responses defined for a project to the design matrix by using the Factor Inclusion or Response Inclusion dialog boxes, respectively, as described in the previous section. Color coding in the column header of the design matrix indicates which role that column plays in the experiment. The default columns have gray headers, any added factors are denoted by yellow background headers, and a pink background header is used for response columns.