What Is a Controlled Experiment

Controlled experiments refer to a scientific investigation in which samples are taken from control groups. The control groups or the experimental groups are exposed to similar variables apart from the factor or factors that are under investigation. This is done so that the effect of the factor(s) can be determined. This is the main aim of a controlled experiment.  It is done with a view of finding out the effect or the influence a single or a few variables have on the test subjects.

Controlled experiments are favored in drug testing. Here the effects of a drug are under the study so that one group; the sample group is given the real drug, while the other group, normally referred to as the control group is given a placebo drug. Scientists are able to study the effect of the drug in the control group using data gathered from both groups. If both groups show similar results, then the drug is ineffective or it is not achieving the desired therapeutic results.

It is through controlled experiments that scientists are able to gather data to be used for comparison purposes. Controlled experiments are part of the scientific method of studying phenomena. It is also referred to as scientific control but it is not experimental in all cases. In cases like astronomy, experimentation might not always be possible, but it still forms a part of scientific control.

In controlled experiments, the factors that need to be controlled are variables as well as attributes. Controlling these factors in the data being collected allows a single and definitive conclusion to be drawn. Conclusions made from controlled experiments are valid and legal science scientists are certain that the data has not been contaminated in any way. The control aspect of the experiment is done so as to avoid confounding variables although this can at times be exceptionally hard. But in a successful controlled experiment, a scientist can claim that a number of situations are identical until a certain factor is introduced resulting in a different outcome.

There are two types of controlled experiments. These are:


These are experiments where the groups in theory should show no phenomena or effect from phenomena. It states that one of the ways to assess the soundness of a theory is to ascertain there is no effect when there should be no effect. In the case of drug testing, a negative control experiment is here a control group is one that has not been administered with the drug. The results would be that he group has shown negative or null effect.


This is a controlled experiment where phenomena are supposed to have an effect on the control group. It is the opposite of the negative form of scientific controlled experiments. These kinds of tests are used to access the validity of tests.