A Trial (or experiment) is a series of runs of the simulation, performed with the same settings for all parameters. The only thing changing are the “random numbers” that Simul8 uses for sampling values from distributions. As the simulation is intended to resemble real life scenarios (i.e. with variability), it is important to run a simulation more than once. A Trial gives you more rounded results and improves accuracy in terms of proposed performance measures (results).
The purpose of a Trial is to check the reliability of results. At the end of just one run you have simulated one week in your organization. You have a result that is from one week. Just like real life, that could have been an average week, or a bad week, or a good week. We have no way of knowing what sort of week it was unless we run a few more of them.
A Trial is a run of several weeks and the trial results summarize the results of these several weeks.
How to run a Trial
To run your Trials, navigate to Home, and then click Run Trials. By default, the number of Runs in a Trial are 5, and Confidence Limits, i.e. the percent to which calculations are accurate is 95%. You can adjust these, and other Trial features by using the Trial Set Up window, available at the drop down under the Run Trials button.
When you run a trial your KPI summary results are displayed as confidence intervals rather than just single numbers.
The central column of figures gives the result averaged across the weeks in the trial. This gives a guide as to what we expect the long term average to be.
The left and right columns give you an indication of how reliable the central (average) figure is. In some cases, the average figure may be very reliable because, perhaps, there is little variation from week to week. In other cases, it may be less reliable. The confidence intervals help you establish how much trust you should put in the single average value. For example, an average of 50 when alternate weeks swing from 0 to 100 is very different, in terms of reliability, from an average of 50 when they vary only between 49 and 51!.
Please note that the right and left values are confidence intervals of the results obtained during a Trial Run. When selecting the 95% limit, these values give you an idea of what the average value is going to be on 95% of the times. 80%, 90%, 98%, 99.8% and 99.9% limits are available by right clicking the mouse on where it says either Low 95% Range or High 95% Range.
The use of a MORE plot
After each Trial, a MORE plot is produced, which is useful for displaying risk and error to support decision making. It is available next to the average and the confidence interval values.
The pointer lines on the left and right indicate the Low and High ranges, and the bars present the frequency of a Result occurring within a Trial. The MORE plot shows how Trial Run results look on a graph, and thus makes it easier for you to examine the variability of your Results.