What is a Randomized Clinical Trial?

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  • Written By: wiseGEEK Writer
  • Edited By: O. Wallace
  • Last Modified Date: 04 January 2020
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A randomized clinical trial is an experimental technique that is designed for the purpose of making results as unbiased as possible. To achieve lack of bias and get a sense of how some form of treatment might work, each person who enters the trial has a random chance of being selected for the different groups that will belong to the study, such as groups that receive a treatment and groups that don’t receive it or receive a placebo. From an experimental standpoint, the randomized clinical trial is often most effective at getting a strong sense of how well a treatment works.

There are other types of experiment designs besides the randomized clinical trial. One form that is similar is randomized block design, where similar groups of people are formed into blocks and then some blocks get the real treatment while others don’t. Alternately, researchers could use something called rigorous control, where each person’s background and history is studied extensively before researchers make up groups based on those findings. Another type of research strategy is to use people who are grouped in pairs because of their similarities, such as twins. These are sometimes called twin studies, and in them, only one twin would receive treatment.


The additional options for experiment design have all been used repeatedly, but still the randomized clinical trial is considered superior. When a suitably large group is tested, it especially avoids an issue called confounding. This occurs when after tests researchers can’t decide what things in the group might have influenced any results. Without randomizing, groups could end up being split by gender or by other means. Innate similarities in a group may make it impossible to determine if it is the treatments or the similarities that created an outcome.

Some other features of a randomized clinical trial may include that the trial is blind, and often double-blind. This means researchers and participants would not know if they were giving or receiving the true treatment. Blinding is effective to eliminate any bias on the part of the researcher, who may want to see evidence of a treatment’s effectiveness and could more positively record any study results. It’s also important to the subject in the study who can’t know if he is receiving the treatment and is less likely to have positive results through hope and imagination.

The purpose of any study is to determine how well how something works or if it works at all. Poor experiment design can thwart that purpose or create confounding so that results can’t be well interpreted. Ultimately, the randomized clinical trial is an effective means to study something while avoiding some of the major pitfalls of poor experiment design.



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