HomeTechniques and Tips@RISK: General QuestionsIterations versus Simulations

2.2. Iterations versus Simulations

Applies to:
@RISK, all releases

Question:
What's the difference between iterations and simulations in Simulation Settings?  Which one should I set to which number?

Response:
An iteration is a smaller unit within a simulation.  At each iteration, @RISK draws a new set of random numbers for the @RISK distribution functions in your model, recalculates all open workbooks or projects, and stores the values of all designated outputs. At the end of a simulation, @RISK prepares any reports you have specified.

For example, if you run 5000 iterations and 3 simulations, then at the end of the analysis you can look at three histograms for each @RISK output.  Each histogram summarizes the 5000 values for the 5000 iterations of one of the three simulations.

For most analyses, you will want N iterations and 1 simulation.  If you use the same set of assumptions for all simulations, you will usually get better results with one simulation of 15000 iterations than with three simulations of 5000 iterations.

But setting simulations greater than 1 is useful in several situations, such as these examples:

Additional keywords: Simtable

last edited: 2013-04-09

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