Control groups are used in scientific experiments to determine the true effects of something being studied. In drug research, double-blind studies are used to test potential effectiveness and side effects. Historical control groups are less accurate. Scientists try to make control groups as similar as possible to the test group. Participants undergo physical exams and questionnaires to ensure similarity.
How does science really know if something is effective or not? Scientific inquiry answered this question a long time ago by trying to create specific controls in experiments. One such measure is the control group, or a group of similar people (animals, plants, etc.) that are observed under the same conditions as the test group, without receiving what the scientist wants to study. By creating conditions as similar as possible for a test and a control group, the scientist can determine the true effects of something he wants to test, eliminating false results, especially if the only substantial variation is receiving or not receiving the thing being studied.
It’s easier to think of the control group in terms of human studies, especially those involving drug research. In a series of so-called double-blind studies, people participate without knowing if they are getting a new drug. The other group gets a placebo and won’t know the study results until much later, if ever.
These clinical trials can reveal a lot about the effectiveness of a treatment and also show when it doesn’t work. For example, a control group not receiving the drug and reporting improved symptoms at a much higher rate than those reported by the group receiving the drug would suggest that the drug may not be as effective as hoped. Not only can the potential effectiveness of drugs be tested this way, but these studies can also show any side effects or long-term problems that could result.
Another way that control groups can be formed is not as accurate and is called historical control. In this scenario the group is actually people who have participated in an experiment in the past, selected as a way to compare results with a group currently under study. Historical control is not always that accurate because theoretically a control group should be as similar as possible to the test group.
In other words, a test cannot use similar samples, because the control group will be very different from the current group. Also, in controlled studies, part of how people try to get accurate results is to try to make the environment the same or similar for all participants. This cannot be done with a previously studied group that forms the control, although a scientist could certainly look for previous control groups that have similarities to currently studied people or other things.
In all human groups, especially in long experiments, it’s difficult to create control groups that look exactly like non-control groups, but scientists have ways of narrowing down what they want. Those participating in the research may undergo lengthy physical exams and fill out multiple questionnaires to ensure they are similar to everyone else in the group being tested. Scientists might exclude participants who don’t show this similarity because additional factors they have could skew test results, making the control group not as effective.
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