Why design experiments?

It has long been recognised that the use of experimental design is crucial in animal research. By using more efficient experimental designs we can maximise the amount of information gained, while reducing the number of animals required. Even seemingly straightforward experiments employ designs that have features that may, in certain cases, help reduce the number of animals. It is also true that if the scientist spends time considering the experimental design, then practical problems can be solved systematically. Experimental design provides a logical framework that will allow the scientist to develop and understand the animal model in a more refined way.

Experimental design is also a useful tool for researchers who do not feel confident running statistical analyses. As observed by Montgomery (1997, p. 18), if you plan the design carefully and correctly, using a little common sense, then the analysis will almost certainly be relatively straightforward. The validity of the results of many statistical tests relies on the underlying experimental design and randomisation.

We shall begin by considering in more detail some of the real benefits to be gained when using experimental designs, from both practical and statistical perspectives. We will then define the fundamental concepts that define an experimental design and finally describe some commonly applied families of designs.