Control Group vs. Experimental Group: What's the Difference?

Key Difference

A control group is a group pf people that do not receive the test variable while an experimental group is a cohort of people that receives variable under testing. Results of experimental group are compared with results of the control group.

Comparison Chart

Control Group Experimental Group
Definition Control group is that group on which researcher is not conducting research or experiment The experimental group is that group of which researcher is doing the research.
Components Test subjects (people, animals, cells, plants, etc.) Test subjects (people, animals, cells, plants, etc.) and variables.
Other Names Placebo group and comparison group Treatment group
Types Positive control group, negative control group
Number of groups Control group is always one group in one experiment. Experimental group can be more than one at a time
Conditions Researchers do not change the values of variables or set a standard value. Researchers change the values of variables to determine the influence of variables.
Overall Effect Control group helps to compare experimental results with non-experimental results. Results of experimental group are compared to results of the control group to determine the influence of variables.


What is Control Group?

A control group is also known as placebo group, and the experiment which uses control group is called a controlled experiment. There is always a variable which has to be tested under an experiment. Control group is a group which is different in an experiment because independent variable being tested do not influence results. It isolates the independent variable’s effects on the experiment and can help rule out alternate explanations of the experimental results. All experiments do not need control group but always need experimental group. But control groups are very useful where experimental conditions are complex and difficult to separate. Control group set on ordinary conditions is most common type of control group in which it does not experience influence of changing variable. Control group increases the reliability and validity of experiment. For example, if you want to explore the effect of salt on plant growth, experimental group would receive salt treatment while control group would not have exposed to salt. Experiments which are conducting on human subjects are more complex. For example, if you are testing a drug whether it is effective or not then members of the control group will be assured that they will not be effected by using this medicine. In this case, a placebo is used in control group. Placebo is a medicine which does not contain active ingredient or agent. In this study, subjects of the control group will not be informed either they are being treated or not. So they have same expectations as the members of the experimental group. This thing eliminates the chances of error in the experiment. But to formulate placebo medicine is difficult and sometimes, it effects the experiment in a different way. Positive and negative groups are two types of control groups in which conditions generates positive or negative results respectively. Positive control group is helpful to show the experiment is functioning as planned while in the negative control group, conditions produce negative outcomes.


What is Experimental Group

An experimental group is also called as treatment group because people or animals of this group receive experimental procedure, test sample or treatment to get results. In this way, experimental group is used to get answers of study under consideration. The experimental group is exposed to changes of the independent variable which has to be tested. Sometimes, experimental group includes multiple experimental groups at one time because different quantity or quality of variable has to be tested. At the end of the experiment, values of the independent variable and results of dependent variables are recorded and used to get results. For instance, if researcher wants to check whether the duration of light exposure has some effects on fish reproduction then control group would be exposed to a normal number of hours of light while the experimental group would be exposed to a different number of hours of light. In this example, light is a variable.


Control Group vs. Experimental Group

  • Both groups have identical composition.
  • A healthy control group is similar to the experimental group in all ways except in the conditions of the experiment.
  • Both control group and experimental group, get observations of researcher for equal time.
  • The experimental group receives treatment while the control group receives no treatment or standard treatment.
  • At the end of the experiment, the null hypothesis will be rejected if there is no difference between results of experimental group and control group.
  • The null hypothesis is accepted at the end of the experiment if there is a significant difference between results of the control group and experimental group.

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