Randomized Experiments
- In an experiment, researchers control the variables by utilizing a control group and an experimental group. This step is essential to establishing cause and effect.
- To ensure that there are no unexpected differences between the experimental and control groups, good experimental design uses random assignment to determine which participants are in each group. This helps to minimize the impact of other variables that the researcher has no control over.
- A well-designed experiment always achieves replication by including large numbers of participants or by repeating the entire experiment with new groups of participants. Replication of experiments increases confidence in the conclusion of the experiment.
In medicine, the randomized experiment (known in this context as a 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.
Another important aspect of a well-designed experiment is that each group is 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.
blinding
Blinding involves keeping participants unaware of which treatment group they’re in to prevent their expectations from affecting the results.
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. This stops people from behaving differently based on what they think should happen. A double-blind experiment is one in which both the subjects and the researchers who have contact with the subjects are blinded.