Introduction

In this chapter we consider experiments on people and animals. Examples are clinical trials, testing educational strategies, psychological experiments, animal nutrition experiments, and trials on ambient conditions in the workplace. There are some issues peculiar to such experiments: these are discussed in Sections 7.2 and 7.7–7.10. On the other hand, the plot structure of such experiments is typically not very complicated, usually being one of those covered in Chapters 6, 4 or 2. These plot structures are specialized to experiments on people and animals in Sections 7.3, 7.4 and 7.5 respectively.

What is an observational unit in such an experiment? Usually it is a person or animal for a set time-period. A measurement may be taken before the experiment starts. This measurement is sometimes called a baseline measurement. It may be used to block the people or animals. It may be used as a covariate in the analysis of the data. Thirdly, the data to be analysed may be the differences between the post-treatment measurement and the baseline measurement.

Sometimes measurements are taken at several different times without changing the treatments. This can be enforced on animals or on hospital patients, but if non-hospitalized patients are asked to come back for measurement too often they may simply drop out of the trial.

What is the experimental unit? It may be a person or animal for the duration of the trial. It may be a group of people or animals for the duration of the trial if treatments can be administered only to whole groups.