[ewilliams]

Two excellent ideas from KPeacock. Also, show your simulation results to your client. It is vital that the client consider them reasonable -- that earns your model validity AND credibility. One validation test, based on this idea, is called the Turing test. How it works (assuming an existing system is being simulated): show the client real system performance metrics (e.g., from last week) and simulation results, but do not say which is which. If the client cannot tell which is which, your model passes the Turing test. If the client can, your model fails the Turing test. In this case, you ask the client "How could you tell them apart?" The client might say, for example "The real system never has a long queue in front of machine X, so the result with the long queue there must be the model one." Now you have a valuable lead for correcting and improving the model.