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How to capture wait time of a queue

When using ProcessModel software, a decision making process improvement tool, there will be a time when you would like to capture wait time of a queue. This capture will allow you to save data that can be further analyzed for process improvement.

In a typical scenario, where you have one entity coming in to the model, then a process (ex: process1) connected to another process (ex: process2), where you want to calculate the time an entity spends at the second process (ex: process2). First we will declare a Real attribute (ex: a_Waiting_Time_in), then we will declare a Real variable (ex: v_Waiting_Time). The attribute (ex: a_Waiting_Time_in) will be used to store time values, while the variable (ex: v_Waiting_Time) will be used to store the time values for further analysis.

Selecting the process (ex: process2) of which we need the wait times of, we go to the Action Logic tab in the properties dialog box, here we will declare the value of the attribute (ex: a_Waiting_Time_in) as simulation clock value, this will store the simulation clock value in the attribute which we will use at the exit route to calculate waiting times (ex: a_Waiting_Time_in = Clock( )). Clicking in the exit route of the waiting process (ex: process2) we will go to the Action Logic tab in the properties dialog box, here we will use the logic to declare the variable (ex: v_Waiting_Time) equal to simulation clock (clock()) and subtracting it from the attribute declared (ex: a_Waiting_Time_in), this will give us the exact wait time (the time the entity spent in the wait process) as the value of the variable (ex: v_Waiting_Time = Clock( ) – a_Waiting_Time_in). Completing the instructions above you should now be able to save waiting time as the value of variable.

To get readable data out of the output report, simulate your model. Once simulation is done, click ‘Show Output Report’. Once the output report is generated, click on the line chart icon that says ‘Generate a time series plot’. In the ‘Choose Statistics for Plot’ window select the variable declared (ex: v_Waiting_Time), add it to the selected values and click OK to see a chart of your data or click export to export the data stored in the variable by every entity processed by the model and display it in an Excel sheet. Once the data is exported to Excel you can manipulate it and use it for generating your own charts or look for areas where processes can be improved.

About the Author:

Scott Baird has been president of ProcessModel for more than 15 years. His focus has been to teach others how to improve processes dramatically. He has been successful in transferring these skills to over 200 companies, including ESPN, NASA, GE, Nationwide, Cendant, SSA and many more. Specialties: Group facilitation for process improvement, process design and simulation, simulation modeling, business management and training others to see opportunities. Scott loves to teach process improvement and has often been heard to say, “Of all the things I do, training others to improve processes is my favorite.” Scott is a father of four and a grandfather of eight. He is an avid woodworker, designing and creating presentation boxes. In his spare time, he volunteers in a college preparation program.

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