The optimisation of systems and processes is an enduring topic for research, development and manufacturing in all sectors of industry. Improvements can be made to specific performance characteristics of technical installations and machines. Or more generally: physical/technical, chemical, medical or business processes can be optimised. Instead of using a "rule of thumb" to look for the correct setting of the input factors impacting a response, a systematic approach is also possible: the method of Factorial Design or Design of Experiments, also known as DoE. This describes the ideal solution for setting up systems so as to achieve the desired responses. This book provides an easily comprehensible description of how DoE works and how this method is used in practice.The book aims to make the principles of DoE intelligible without resorting to complicated mathematics and to present compact calculation rules. The reader thus gains the confidence to parameterise the DoE software correctly and interpret the outputs properly. The numerical examples used can be downloaded from the Internet as Microsoft Excel(R)/OpenOffice Calc(R) files.The book was written for practitioners in all disciplines and all sectors of industry who wish to systematically optimise technical installations, products, and processes. It also serves as a textbook and reference work for students of the natural sciences/engineering, medicine, social sciences or business studies.