What is a Randomized Controlled Trial?

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  • Written By: Debra Durkee
  • Edited By: Daniel Lindley
  • Last Modified Date: 08 March 2020
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A randomized controlled trial is a common method that scientists and researchers use to conduct tests and experiments with living subjects. Two groups are organized that are as identical as possible, with one difference between them. This difference is the variable measured. The test format is commonly used when medical professionals are evaluating the success of a new drug or method of treatment.

There are typically a large number of participants in a randomized controlled trial. This helps give a wide range of variable effects, including successes, failures, and side effects. Typically, in a medical trial, some of the participants are given the drug to be evaluated and the other half of the group is given a placebo. When the participants do not know if they are taking the real thing or not, there is no bias or preconceived notion on whether or not they will see a difference in their symptoms and health.


Another advantage to using the randomized controlled trial method in medical studies is that since there are a large number of participants with the condition being treated, researchers can see how the medication or treatment will react in a variety of individuals. While cases might be similar, the individual makeup of participants vary; some may have other conditions that may impact the outcome, while others may react with different side effects or allergies. As it is important that each group not know if it is taking the real medication or the placebo, both groups of participants typically receive the same care and monitoring, aside from the medication being tested.

In some cases, a randomized controlled trial can take years to complete. In order to study the long-term effects of some treatments, participants may be a part of the trial for decades. The disadvantage to this is that while it can be thorough, it can also prolong the release of medications or treatments to the general public. It also relies on the continued participation of those who have volunteered, and can be very time consuming on the part of the researchers.

There is also the question of treatment for the placebo group. In order to truly determine the positive or negative effects of the drug being tested, the only difference between groups of a randomized controlled trial should be the administration of a drug. For the placebo group, this can result in these individuals not getting treatment that may, in the long run, be beneficial to them.



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