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-effect relationships and quantify them at least summarily (for example, the effect of temperature on the viscosity of a polymer).

Various tools can be used for this research, including :

• fault tree or cause tree ;

• cause-effect diagram (also called "fishbone" or "Ishikawa" diagram);

• correlation and regression studies ;

• experience plans ;

• data analysis: principal components...