Terminology Experimental Design (II)

In terms of the experiment, we need to define the following:

Treatment: is what we want to compare in the experiment. It can consist of the levels of a single factor, a combination of levels of more than one factor, or of different quantities of an explanatory variable.

Experimental unit: is the physical unit that receives a particular treatment, for example, a plot in the field. It is essential that the allocation of a treatment to a particular experimental unit is at random.

Measurement unit: the level at which observations are made, usually one measurement per experimental unit, but it is possible to make more than one observation within a single experimental unit (repeated measures).

Replication: is the number of independent instances of a treatment that occur within an experiment i.e. several experimental units receive the same treatment.

Block: is a group of experimental units that show some similarity/homogeneity between each other. Random allocation of treatments to units within blocks reduces experimental error.