Name:
_______________________________________________
Hand in the next two pages with answers to the following:
From Step 8:
Total number of applications served during the simulation:___________
Maximum flowtime of applications:_______________
Maximum number in Application Review queue: ____________________
Average time in the Application Review queue: _____________________
Average number in the Application Approval queue: __________________
Average time in the Application Approval queue: _____________________
Minimum time in the Application Approval queue: ____________________
Average Utilization of the Loan Officer: ____________________
From Step 10
:
Using the Expression Editor, what is the plot expression being used for number in Applications Review queue:
____________________________________
From Step 16: Have the Instructor or TA see your animation of the entities, queue, and resource, demonstrate the use of views, and illustrate your great banner and check-off here: _____________________________
From Step 20
:
What is the overall average Production (compute the average manually)?
_____________________________________________
From Step 23: What is the confidence interval for average Production produced by
Arena?
_____________________________________________
From Step 27: What is the impact of this change on the system in terms of:
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(c) flow time: ______________________________
(d) queues: _________________________________
Step 27: After re-running the simulation, what is the impact of this change on the system in terms of:
(a) Production: __________________________
(b) flow time: ______________________________
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Lab Purpose: Gain experience with Arena in building of a simple model “from scratch” and examine its output. Understand modeling is an iterative process.
Simulation Problem: Student loan applications are processed by two people in the
Student Loan Office. First the loan Review Clerk examines the loan details and determines if the application is complete. If the application is complete, then the
Loan Officer examines the application to determine if the application satisfies all the criteria for a loan.
Applications arrive about every two hours randomly. Typically, the time for the loan review is one and three-fourths hours, while minimum service time appears to be about 1 hour and maximum service time is about 3 hours. The time for the loan approval is Lognormal distributed with a LogMean of 2.25 hours and a LogStd of
.75 hours.
Simulate the system for 40 consecutive eight-hour days.
First, construct a Conceptual model
What do the entities represent? _______________
What do the resources represent? _______________
Draw a flowchart in the space below of the applications arriving, being served, and leaving. Put the data associated with each process on the block diagram elements:
Step 1: Bring up Arena and start a new model. Attach the Basic Process Panel (if it is not already attached).
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Step 2: Place a Create flowchart module on the model canvas. Put in the interarrival time specifications and other information in the dialog.
Step 3
:
Place two consecutive Process flowchart modules on the model canvas: one for the Application Review and the other for Application Approval. Specify the resources and the service times. Make sure the queue information is correct in the
Queue spreadsheet module.
Step 4
:
Place and specify a Dispose flowchart module.
Step 5
:
Be sure that the various Modules are connected – use the connect tool.
Make sure the “animate connector” button is pushed.
Step 6
:
In the Run->Setup specify Title, Analysts, date. Make the length of the simulation 40 eight hour days. Specify the base time units.
Step 7
:
Execute the simulation.
Step 8
:
From the Reports, write down:
Total number of applications served during the simulation:___________
Average flowtime of applications:________________
Minimum flowtime of applications:_______________
Maximum flowtime of applications:_______________
Average number in the Application Review queue: __________________
Maximum number in Application Review queue: ____________________
Average time in the Application Review queue: _____________________
Minimum time in the Application Review queue: ____________________
Maximum time in the Application Review queue: ____________________
Average number in the Application Approval queue: __________________
Maximum number in Application Approval queue: ___________________
Average time in the Application Approval queue: _____________________
Minimum time in the Application Approval queue: ____________________
Maximum time in the Applications Approval queue: ___________________
Average Utilization of the Loan Review Clerk:______________________
Average Utilization of the Loan Officer: ____________________
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Step 9: Use the Plot Animate tool to plot (see Step 10 to determine the plot expression):
(a) number in Applications Review queue
(b) number in Applications Approval queue
(c) the number busy of Review Clerk
(d) the number busy of Loan Officer
Step 10
:
Using the Expression Editor, what is the plot expression being used for number in Applications Review queue:
____________________________________
Step 11
:
Run the simulation and answer the following by looking at the plot:
Does number in Applications Review queue increase or decrease with time?
_________________________________
Does number in Applications Approval queue increase or decrease with time?
_________________________________
Does the Review Clerk utilization increase or decrease with time?
_________________________________
Does the Loan Officer utilization increase or decrease with time?
_________________________________
Step 12: Using the View menu item, create three “views” of the model. Below are the “hot keys” and what the view should show (use the Arena “help”):
(a) view “o”: see overview of everthing
(b) view “m”: show model logic (just the flowchart modules)
(c) view “p”: show plots
(d) view “a”: animation only
Step 13: Use the Resource Animate tool animate the Idle and Busy states of the each resource. Use the picture library from c:\Program Files\Rockwell
Software\Arena\. Picture libraries have the extension .plb. Choose representations from these pictures. Be sure the “seize area” is checked and location. Size the pictures appropriately.
Step 14: Use the Entity module to add a picture for the entity. Size the pictures appropriately.
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Step 15
:
Put a title and your name in white on a red background as a banner to the simulation using the drawing facilities within Arena.
Step 16: Show off your animation of the entities, queue, and resource, demonstrate the use of views, and illustrate your great banner: sign-off on hand-in pages.
Step 17
:
Change the Simulate module to make five replications.
Step 18
:
Execute the simulation (be sure to use “fast-forward” to avoid having to watch the animation).
Step 19
:
Write down the five average values for each replication/run below:
Run 1 Run 2 Run 3 Run 4 Run 5
Production
(Applications competed)
Step 20
:
What is the overall average Production (compute the average manually)?
_____________________________________________
Step 21
:
What is the standard deviation of the average Production (compute manually)?
_____________________________________________
Step 22: Compute the 95% confidence interval for average Production manually?
( t
4,.975

2.776)
_____________________________________________
Step 23: What is the confidence interval for average Production produced by Arena?
_____________________________________________
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Step 24 : Ignore now the animation and work only with the simulation model and the plots. The Loan Approval appears to be a bottleneck. The Loan Officer is overburdened and the Loan Approval queue is large. Let’s consider some changes.
Step 25: It is observed that 18 percent of the loan applications are incomplete and do not have to be reviewed by the Loan Officer. The Decide flowchart module can be used to “branch” entities. Use it to branch only 82 percent of the entities form the
Application Review process to the Application Approval process. Put the remaining
18 percent into another Dispose module.
Step 26: Rerun the simulation (one replication of 40 eight hour days).
Step 27: What is the impact of this change on the system in terms of:
(a) Production: __________________________
(b) flow time: ______________________________
(c) queues: _________________________________
(d) resource use: ____________________________
Step 28: Closer examination of the Application Approval process reveals that the processing time follows a more complicated form than first thought. The proper time is given by the following expression (in hours): (1 / (1+Number in Approval Queue))
* (Normal whose mean is 2.5 and whose std dev is .7). Use the Expression Builder to enter this value into the Delay time expression of the Application Approval process.
Step 27: After re-running the simulation, what is the impact of this change on the system in terms of:
(a) Production: __________________________
(b) flow time: ______________________________
(c) queues: _________________________________
(d) resource use: ____________________________
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