Experimental controls are used in all accurate scientific experiments. Using an experimental control in an experiment involves in setting up a control groups i.e. a groups that have not been changed in any way by the experiment. These control groups are useful to derive baselines measures or observations used for evaluating the results of an experiment. Controls are used so that an experimenter can compare the group that has changed to the group that stayed the same.

An example: consider an experiment to study the effect of low carbohydrate diet on the general metabolism of subjects. To have a baseline measure we set up a control group which is fed with ordinary diet and have other groups which are fed a low carb diet (the experimental group). Generally several control groups must be set up in order to get a better understanding of the phenomenon under study and unbiased results. Suppose the control group that the scientist has set up consists of football players. Their general metabolism would be far higher than the other group and this may lead to biasing of results. This was an obvious cause but there may be many latent ones. Variables which must be fixed or controlled because of potential interference with experiment are called confounding variables.