1. Process parameters and product characteristics to be controlled

1.1 Process parameters

To control a process, it is necessary to work on the parameters of that process rather than on the characteristics of the product, i.e., to identify cause-and-effect relationships and quantify them at least roughly (for example, the effect of temperature on the viscosity of a polymer).

Various tools can be used for this research, including:

• failure tree or cause tree;

• cause-and-effect diagram (also known as a "fishbone diagram" or "Ishikawa diagram");

• correlation and regression studies;

• experimental designs;

• data analysis: principal components...

...