Design of experiments is concerned with optimization of the plan of experimental studies. The goal is to improve the quality of the decision that is made from the outcome of the study on the basis of statistical methods, and to ensure that maximum information is obtained from scarce experimental data.
If the decision making process is based on statistical hypothesis testing (e.g. on analysis of variance), then the goal is to increase the power of the statistical test. If the decision making process is based on estimation of the parameters of interest (e.g. using regression analysis), then the goal is to increase the precision of the estimates of the parameters derived from the outcome of the experiment.
The term”design” is also used to refer to the specific plan of the experiment that has been obtained in course of the designing procedure. See, for example, crossover design, parallel design, self-controlled design, complete block design.