Control Variables: Definition Examples and Methods

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Control Variables: Definition Examples and Methods
Post By tapaflcouk On 27, Dec

The progress of scientific studies has always been dependent on variables. It is the variables that yield the results of a research study. As a researcher, you might only know about dependent and independent variables. The relationship between them is actually the results of your research study. However, there is one more variable called the Control Variable. Although this variable does not take part in the study directly, it is necessary to know. Considering this variable is essential to approve a hypothesis and protect the study from bias.

Do you know what a Control Variable is? Most probably not, because if you knew, you would not be here reading this article. Well, there is no need to ponder a lot on this. In this post, we are going to uncover all the details about this variable in scientific studies. From definitions to examples and methods to control a variable, we will discuss everything. So, let’s start with the definition of this third and crucial variable.

What Is A Control Variable In Research?

A variable held constant or limited during a scientific study is known as the Control Variable. Keeping such a variable constant is necessary for a research study. It is because although it is not of interest to research aims, still, it can influence the outcomes or results of the study. As a researcher, you always try to keep such a variable constant using different techniques. Also, to determine the exact relationship between dependent and independent variables, it is necessary to control any extraneous variable that can harm the study.

What Is The Importance Of A Control Variable?

Although it is not related to the research aims, still, it can have a significant impact on the results of a scientific study. This is exactly why controlling such a variable is necessary. However, it is just one point that explains its importance. Some other points are given as follows:

  • The control is important. It is because it allows you to measure the exact relationship between independent and dependent variables.
  • Another point that shows its importance in a research study is that if you do not control extraneous variables, your results may get faulty.
  • Having an idea of such variables and how to control them allows you to reproduce the experiment.
  • Control variables are extremely crucial. It is because they enhance the internal validity of your research study and make the results more valid.

Using The Control Variable In Different Research Studies

After reading the information above, you now have a good idea of what it is and why it is important. Now, we will look at its usage in different research studies, e.g., experimental and non-experimental. Hence, without wasting any time further, let’s see how they are used and how they affect the results of a scientific study.

In Experimental Studies

In experimental research studies, you aim to measure the effect of the independent variable on the dependent variable. For this, you manipulate the independent variable and see what changes the manipulation brings to the dependent variable. Such variables in experimental studies make sure that the results are fair and free from any kind of bias. How? It is because you can control the extraneous variables in the lab and can minimise their impact to a large extent.

In Non-Experimental Studies

Any study that does not involve the use of experiments and makes use of techniques like observation is non-experimental. A control variable plays a crucial role in non-experimental studies. It is because, in observational studies, you cannot manipulate the independent variable. It is not under your control. However, you can monitor its effect on the results and keep it to a minimum level.

Some Examples Of Control Variables

Anything you can measure about the research study which is neither related to the independent variable nor the dependent variable is a Control Variable. The information given above must have strengthened your theoretical knowledge about such a variable. Now, let’s strengthen the practical knowledge. Hence, some top examples are as follows:

Research Questions Control Variables
Does this tablet reduce headaches? Age & Health
Are weight loss programs in the UK effective? Activity levels

Starting weights

Does the baking temperature affect the quality of the clay pot? Type of clay

Clay moisture

Is the use of caffeine improve memory recall? Participant age

Type of memory test

Does the quality of the soil affect plant growth? Temperature

Amount of water

Difference Between Control Variables And Control Groups

Many researchers like you confuse the term control variables with control groups. For your information, both controls are different from each other. It is because control groups are mostly governed by constant variables. In simple words, you can say the control group is a mini-sub-sample. Do you know about the differences that exist between them? No. Thus, below are the major differences between a control group and a control or constant variable:

The Difference in the Consistency

The first difference that exists between this variable and the control group is the difference in consistency. Such variables remain constant during the whole study. As a researcher, you do not try to manipulate because the internal validity depends on them. On the other hand, control variables govern the control groups. They may change depending on the variables.

The Difference in the Creation

The second difference is related to the method of creation of such variables and groups. Control variables are derived from the research questions formulated at the start of the study. They do not depend on the sample population or respondents. In the meantime, control groups are dependent on the population. The groups are only created by considering the population.

The Difference in the Purpose

Lastly, the 3rd difference that lies between control or constant variables and groups relates to the purpose. Both serve different purposes in a research study. The control variables set a base value for the measurement of the relationship between independent and dependent variables. On the other hand, the control groups develop a frame of reference for other samples. Thus, both control variables and groups are on different missions.

Methods To Control A Variable In A Scientific Study

There are different methods in practice to control a variable when studying a particular topic. However, three methods are very commonly used. Do you have an idea of those three methods? Most probably not. Thus, a brief description of those three methods is given as follows:

Random Assignment

The first method of controlling a variable is known as random assignment. This method is mostly used in experimental studies to control a variable. Furthermore, this method of controlling a variable is particularly useful where there are multiple groups. Each group’s participants have different characteristics. Random assignment helps you balance the properties of groups and control variables effectively.

Statistical Controls

Sometimes, controlling all the variables and removing their influence on the results is impossible. It mostly happens in non-experimental studies, where a Control Variable is not in your hand. In such a case, you can apply the technique of statistical control to limit the research bias. This method works by applying modelling, weighting, and averaging techniques. Thus, the use of this technique provides you with a more realistic picture.

Standardised Procedures

Lastly, the next technique to control a variable is known as standardised procedures. It works on the same principle of a daily routine of a human. This method asks you to use a standard procedure for all the groups involved in the study. As the researcher, you must not use one method to study one group and a different method to study the second group. The experimental procedure and method must be the same for every group.

Frequently Asked Questions (FAQs)

What Is A Control Variable?

Simply put, it is a variable in a research study that is held constant. It does not have any relation to the research aims and objectives. However, it is a variable that has the potential to harm the outcomes of the research study.

Why Do We Control Variables?

Control variables enhance the validity of the research study. Also, they make sure that the results obtained after the study are not faulty and answer the research questions. Due to these two primary reasons, we control them in a scientific study.

What Is Internal Validity?

Internal validity is the extent to which you are confident that the relationship between the variables cannot be described by other factors. Internal validity and control variables have a close relationship. The more you control them in the study, the more its internal validity. So, this is what it means by the term internal validity.

Final Thoughts

To sum up, experimentation or research study is not as simple as you think. It is not just about changing one factor and getting the results. There are many players or variables in a research study that you need to consider and control. An example of such a variable is a control variable. It is a variable held constant throughout the research study. In this guidepost, we have discussed everything related to control variables, from methods of controlling to examples. So, you must not miss reading a single line written above and follow the methods.

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