Components of Experimental Design

Randomized Experiment

In medicine, the randomized experiment (clinical trial) has become the gold standard for the evaluation of new medical treatments because of its effectiveness and ability to objectively support conclusions. The Cochrane Collaboration is an organization devoted to synthesizing evidence from medical studies all over the world. According to this organization, there have been hundreds of thousands of randomized experiments comparing medical treatments. In most countries, a company can’t get a new drug approved for sale unless it has been tested in a well-designed experiment. A good (well-designed) experiment will randomly assign the experimental units to the treatments.

Blinding

Another important aspect of a well-designed experiment is that each group be treated the same way. It is also important that the subjects do not adjust their behavior because of the treatment they are receiving. For this reason, many experiments use a technique called blinding. When a person involved in a research study is blinded, they do not know who is receiving the active treatment(s) and who is receiving the placebo treatment.

blinding

Blinding is the nondisclosure of the treatment an experimental unit is receiving, as to preserve the power of suggestion in a randomized experiment. 

 

A double-blind experiment is one in which both the subjects and the researchers who have contact with the subjects are blinded.

Replication

Replication is another key component in a well-designed experiment. Replication helps to ensure that the results of an experiment are truly caused by the change in the factor of interest and not by other hidden factors or natural variation in data. A well-designed experiment always achieves replication by including large numbers of participants. Replication can also be achieved by repeating the entire experiment with new groups of participants. Replication of experiments increases confidence in the conclusion of the experiment.