Randomized Complete Block Design

The Randomized Complete Block Design (RCBD) probably is the most used and useful of the experimental designs. This design takes advantage of grouping similar experimental units in blocks or replicates. The blocks of experimental units should be as uniform as possible. The purpose of grouping experimental units is to have the units in a block as uniform as possible so that the observed differences between treatments are largely due to differences between treatments. Then, treatments are randomly assigned to the experimental units within each block so that each treatment occurs with the same frequency (usually once) in each block; that is, each block contains all treatments. The blocks generally represent levels of natural differences or sources of variation that are not related to treatments. In the analysis of variance (ANOVA), the variation between blocks can be divided from the experimental error, thus reducing the mean square error (MSE) and increasing the power of the test.