Doing performance modeling as a consultant, the biggest problem we had wasn't building the model, the devil was always in the model's validation. How do you know that the model is connected to reality? This issue was such a common occurrence that I named it the Excel Syndrome. I don't know if you've noticed, but Excel spreadsheets are this way. You may have all the formulas right, but those who haven't built it, or reviewed it in every detail, have little faith in the results. All modeling is this way, even fun simulators with fancy animations.The Excel Syndrome is such a basic truth that it extends way beyond modeling.
Let's take a look at The Scientific Approach to Innovation!