Separate experiments to assess the effects of two factors

Sometimes the response of interest is influenced by two or more factors, each of which can be controlled in an experiment.

The simplest way to study two factors is with two separate completely randomised experiments. In each of these experiments, one factor is kept constant (e.g. the colour of an artificial flower) and the other factor is varied (e.g. the flower's shape). However this is an inefficient way to assess the effect of the two factors.

A complete factorial experiment therefore estimates the effects of two factors as accurately as two completely randomised experiments involving double the total number of experimental units.

Blood pressure after an operation