ABSTRACT
The split plot is the prototype nested design, encompassing the primary features of nesting with two or more factors. It helps to examine subsets of the experiment to learn about the design and about how to analyze the data to address key questions. Split plot designs arise commonly in agriculture, industry and across the biological sciences. They have a two-way or higher-way treatment structure arranged in incomplete blocks, with one or more treatment factors assigned across blocks and the rest assigned to smaller units within each block. The split plot experiment can be viewed as a particular form of mixed model with two random effects and a two-factor structure of fixed effects. Estimation of variance components and fixed effects follows along already developed lines for mixed effects models. The smaller units, sometimes called 'split plots' or 'subplots', are the experimental units for factors assigned within block by subplot.
