Variability with respect to dimensions, material properties, loads and other associated boundary conditions leads to greater uncertainty in actual design performance. If you could incorporate realistic uncertainty into use your existing Finite Element Models, your simulations would be able to quickly find acceptable, real world solutions instead of arriving at optimal, but sometimes fragile configurations. This would allow you to design systems that better meet user-specified performance, and improve overall product quality with less reliance on physical evaluation. In other words, effectively manage risk associated with your designs using Virtual Product Development techniques. This is exactly what MSC.Robust Design can help you do.