Some Simple Experimental Designs

In the previous chapters we developed techniques suitable for analyzing experimental data. It is important at this point to consider the manner in which the experimental data were collected as this greatly influences the choice of the proper technique for data analysis. If an experiment has been properly designed or planned, the data will have been collected in the most efficient manner for the problem being considered. Experimental design is the sequence of steps initially taken to ensure that the data will be obtained in such a way that analysis will lead immediately to valid statistical inferences. The purpose of statistically designing an experiment is to collect the maximum amount of useful information with a minimum expenditure of time and resources. It is important to remember that the design of the experiment should be as simple as possible consistent with the objectives and requirements of the problem. The purpose of this chapter is to introduce some basic principles of experimental design and discuss some commonly employed experimental designs of general applications.