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Randomized Controlled Studies

A randomized controlled study is one in which:

  1. There are two groups, one treatment group and one control group. The treatment group receives the treatment under investigation, and the control group receives either no treatment or some standard default treatment.
  2. Patients are randomly assigned to all groups.
Assigning patients at random reduces the risk of bias and increases the probability that differences between the groups can be attributed to the treatment.

Having a control group allows us to compare the treatment with alternative choices. For instance, the statement that a particular medication cures 40% of cases tells us very little unless we also know how many cases get better on their own! (Or with a different treatment).

 With certain research questions, randomized controlled studies cannot be done for ethical reasons. For instance, it would be unethical to attempt to measure the effect of smoking on health by asking one group to smoke two packs a day and another group to abstain, since the smoking group would be subject to unnecessary harm.

 Randomized controlled trials are the standard method of answering questions about the effectiveness of different therapies. If you have a therapy question, first look for a randomized controlled trial, and only go on to look for other types of studies if you don't find one.



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