A statistical modeling tool is presented that enables real-time viewing of how changes in method, process, and stability variability/bias impact product acceptance rate. The tool can be used to set and justify specifications. As needed, additional sources of variability/bias can be added to further optimize the tool’s prediction power. The tool can be used to assess each manufacturing run to ensure the process is in control. Aberrant results can then be investigated to see what source of variability/bias may have changed. To enable continuous improvement, the impact of new processes, methods, or technologies can also be addressed and such changes justified. | Process and method variability modeling to achieve QbD targets