Main Principles of experimental design: the 3 “R’s”
There are three basic principles behind any experimental design:
Randomisation: the random allocation of treatments to the experimental units.
Randomize to avoid confounding between treatment effects and other unknown effects.
Replication: the repetition of a treatment within an experiment allows:
To quantify the natural variation between experimental units.
To increase accuracy of estimated effects.
Reduce noise: by controlling as much as possible the conditions in the experiment. A classical example is the grouping of similar experimental units in blocks.
Using known characteristics/properties of the experimental units to explain variation, for example inclusion of block effects in the statistical model.