Figure 8.

Schematic of a completely randomised design to study milk production in dairy cows. In this completely randomised design, there is one factor of interest (diet with two levels: diet A or diet B). The individual cows are randomly allocated to a diet and milk production subsequently measured three times in the last week of the following month (allowing several weeks for the animal to adjust to the new diet). In this design, the cow is the biological unit and the experimental unit. The observation unit is the measurement of milk production on a day for a cow. As shown in the diagram, to account for this repeat measure structure, the average milk production is calculated prior to the statistical analysis.