In-depth design analysis and simulation are typically used as a means to assess the performance of a part or a system for one given set of CAD dimensions, loads and material properties.
However, simulation can also be used as a way to answer "what if" questions: What happens if my load changes by 10%? Which parameters are really influencing the behavior of my system? These types of questions can be answered by an appropriate parametric study of the model.
A parametric analysis can be either deterministic or probabilistic. In the former case, all parameters are supposed to vary continuously within a given range (defining the design space) and the expected result is the continuous response of the various performances. The deterministic analysis is a first step to take to understand the product and find a feasible design within the design space. Once a feasible design has been found, the next question is: how robust is it?
The probabilistic parametric analysis will help answer that question. Loads, dimensions and material properties are not deterministic parameters; a dimension has a certain tolerance and material properties depend on the manufacturing process. How does the scattering of these parameters influence the performance of the product? How much is the product likely to fail?