The Role of Design in Experimental Investigations

The three basic principles of experimental design, namely replication, randomization, and local control, are briefly discussed. Advantages of the proper application of the principles are given, and the importance of the role of experimental design is illustrated by a numerical example. Three analyses are performed on the same set of test data. First, an analysis is performed on a set of empirical data to salvage as much information as possible from the data of the uncontrolled experiment. Secondly, some but not all information is obtained about the conduct of the experiment, necessary assumptions are then made, and an analysis of variance is performed. Finally, the data are properly analyzed by performing a nested-factorial analysis of variance as dictated by the design and the actual conduct of the experiment. The validity and the amount of information resulting from the three analyses are then compared.