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Welcome to this month's newsletter! In this issue you'll find:
And don't forget, you can always tell us what you think of our newsletter by emailing newsletter@SIMUL8.com.
Simulation Results: What Information should I Collect? by Professor Stewart Robinson of Warwick Business School
We develop simulation models to better understand the systems we are modeling and to try and find ways of improving those systems. In developing these models we often spend much time thinking about what aspects of the system to model, but we may spend less time thinking about the information we want to obtain from our models.
SIMUL8 provides many results automatically and also gives opportunity to collect your own customized reports. The danger is, if course, that you get swamped by the amount of information the model is giving. So how can you choose which are the most important results to look at?
This can be answered by thinking about the purpose of the results you are obtaining from your model. Broadly speaking, there are two reasons for looking at the results. First, you often have some objective in mind when carrying out experiments with a model e.g. improved throughput or reduced waiting times. You need to look at results that specifically tell you whether you are achieving your objective. In these examples the answer is somewhat obvious: throughput and waiting time.
The second reason for looking at results is to understand why you are not achieving your objectives, assuming, that is, you are not achieving them. Such results are a little more difficult to identify. You need to think about what results would point to problems in a system. Typical things to think about are identifying bottlenecks or resource shortages. How can a bottleneck be identified? Normally by looking for a build-up of queues and work centers that have a high utilization. A shortage of resources can be identified through high resource utilizations and queues before the points where those resources are employed.
Having identified the results that you are interested in, you also need to think about how to present those results. Useful ways of presenting results are as follows:
- Cumulative total and percentage :
e.g. total throughput or percentage utilization over a simulation run.
- Mean and standard deviation :
e.g. the average queue length. The standard deviation provides a measure of the variation around the average.
- Median and quartiles :
the median identifies the most central value. Quartiles provide an understanding of the range of values.
- Mode :
the most likely value. Particularly useful if the system you are modeling is only going to happen once e.g. a concert. In this case knowing the mean performance is of little use as this can only be achieved if you repeat an event many times.
- Minimum and maximum :
providing an understanding of the full range of the results.
- Time-series :
a very good way of understanding how a value changes over time.
- Bar charts :
provides a clear understanding of the variability of a value.
- Scatter diagrams :
showing the relationship between two values e.g. resource utilization and customer waiting times.
Graphs are particularly good for identifying patterns in the results, while numbers are useful for understanding the detail of the results. As such, it is useful to use a range of methods for presenting your results.
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Professor Stewart Robinson is a world renowned expert on simulation. Take a look at his book Simulation: The Practice of Model Development and Use .
It's a non-technical textbook that concentrates on discrete event simulation as it is used in operations management. It takes you through the key stages in a simulation project in terms of both the technical requirements and the project management issues surrounding it. It will help you develop appropriate valid conceptual models, perform simulation experiments, analyze the results and draw insightful conclusions. |
New SIMUL8-Planner Website
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The SIMUL8-Planner website has been given a fantastic new look. Check it out to find lots of information about how SIMUL8-Planner uses simulation to create an adaptive scheduling and planning solution. Also read about how SIMUL8-Planner has been applied on the shop floor already. |
Free Downloads
A new service pack for SIMUL8 2006 Build 1102 has been released.
Download the Service Pack | Full Details of What's in the Service Pack
A new service pack for SIMUL8 2005 Build 1102 has been released.
Download the Service Pack | Full Details of What's in the Service Pack
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newsletter then email Newsletter@SIMUL8.com
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