An essential element in development is successfully applying findings derived from scientific experiments. More often than not, designs for comparative experiments include an experiment group and a control group composed of subjects from the same sampling frame.

To conduct any form of comparative experimental analysis effectively, we must try to understand the role played by a control group.

What is a control group?

When researchers want to test something, they usually choose a group of people who are similar in important ways, such as age or gender. From that group, they pick two smaller groups: one that will receive the treatment they’re testing (the treatment group) and one that won’t (the control group). They make sure to remove any factors that could affect the results so that they can see if the object of testing really makes a difference.

The American Psychological Association (APA) gives a control group definition as a group of people that is used for comparison in an experiment. Control groups either get no intervention or standard placebo treatment, whereas the experimental group gets the treatment being tested. This helps researchers see if the treatment actually works and not just because of other factors.

The results from the control group form a base to which the results from the experimental group are compared.

Why is a control group important?

Simply put, a control group is there to allow reliable research to take place by providing a threshold against which experimental results can be analyzed and the effects of the intervention measured. Without it, it would be impossible to trust research findings reliably.

What are the advantages of a control group?

Some of the general advantages that a control group serves are:

• Provides a baseline

Results from the control group act as the standard against which the effects of the treatment or independent variable, as seen in the experimental group, are measured. Without it, it would be hard to judge whether the changes in the experimental group were due to intervention or other variables.

• Eliminates bias

Being identical to the experiment group in terms of all aspects, demographic and otherwise, the control group makes it easy to determine whether the results obtained are due to the treatment only and not a result of a biased selection of subjects influenced by different variables.

• Increases reliability and validity

Due to the points above, a control group inevitably creates the reliability and validity of the research being conducted. However, it must be ensured that the control group is randomly selected to ensure external validity.

• Supports decisions based on evidence across disciplines

From psychology to public policy, there are several effective control groups in research examples. Even during the policy-making processes, a governing body may be able to assess the efficacy of a return by comparing its effects on a treatment group to a control group.

• Limits possibly harmful interventions

Control groups allow researchers to quickly gauge an intervention that does more harm than benefit and limits its use to only the experiment group.

The possible advantages of a control group are endless. Control groups that receive a placebo even allow us to measure the placebo effect. Let’s look at the different types of control groups.

What are the different types of control groups?

Various factors, including but not limited to ethical considerations, the research aims and limits, and the nature of the independent variant, determine the kind of control group that will be selected. Some common control group types are as follows:

• Placebo control group

This group comprises subjects who have received a placebo treatment, and it helps researchers measure the extent of the placebo effect or the perceived effectiveness of a treatment that is ineffectual.

• Active control group

In this case, some subjects get a different or usual treatment. This helps researchers see if one treatment is better than the others and if other factors like support or the subjects’ condition affect the results. An active control group in research example is when the government wants to see how a policy affects a specific group of people, like those living in cities or rural areas.

• Historical control group

A historical control group is when researchers use data from a previous study instead of recruiting new people for their current study. They use information from people who are similar in important ways, like age or gender, and who received the same treatment in the past experiment. This helps save time and resources.

• No-treatment control group

Herein, individuals like those in the experiment group are not subject to any intervention at all. This group establishes a true baseline with which findings can be compared. Think of the time when the COVID-19 vaccine was being developed, and you’ll find another useful control group in research example.

What is a control group example?

Apart from the examples from disciplines shared previously, an important question that one needs to delve into in the modern world is, what is a control group in psychology?

In the early 1900s, a series of experiments were conducted at the Hawthorne Works factory to understand the effects of environmental factors on the productivity of employees. Herein, the experiment group was placed in a well-lit room and given creation tasks to perform.

They received increased support from the researchers and regular breaks. However, a control group of employees was set up in the same facility but in a poorly lit room and received no support or breaks during their tasks. The results of both groups were compared to verify the Hawthorne effect that stipulates that a positive environment has a positive impact on productivity.

Another effective example is a company considering making a change in the vacation days granted to employees to enhance their productivity. A viable way to do this would be to pit a control group vs experimental group, where the experimental group is granted a few more vacation days and the control group is not. An analysis of the productivity of both groups following this announcement would allow executives to decide whether this change will have a positive impact or not.

Did you know?

The use of control groups in scientific research dates back to the 18th century when the Scottish physician James Lind conducted a controlled experiment to determine the effectiveness of different treatments for scurvy. At the time, scurvy was a common and deadly disease among sailors on long sea voyages, and there was no widely accepted treatment for the condition.

Lind used a controlled approach by dividing 12 sailors into six groups and assigning each group a different treatment, with one group receiving seawater as a control. His findings showed that citrus fruits were an effective treatment for scurvy.

This experiment is a classic example of controlled trials in medical history, and it established the importance of using control groups in scientific research. Today, randomized controlled trials are the preferred method of testing the effectiveness of interventions, with control groups being a critical element of these trials.