Mastering Control Variables in Research: What You Need to Know


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Table of Contents
Control Variables1

A control variable maintains a consistent state throughout an experiment or research, aiding the examination of relationships between various variables. Its stability ensures fair comparisons in test results and prevents any distortion, enabling researchers to gain clearer insights into variable relationships.

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Control Variables2

In research, scientists use control variables with independent and dependent variables to analyze data. This practice aids researchers in isolating the effects of variables apart from the primary ones under study. Researchers have the ability to directly or indirectly manage these factors.

Direct control involves maintaining variables at a constant level throughout the research or experiment, such as stabilizing temperature conditions. Indirect control methods, on the other hand, utilize statistical techniques to manage variables.

What is a control variable?

Control Variables3

Control variables, also called constant variables, are parts of an experiment that researchers keep the same on purpose. These factors are important in making sure that outside influences do not affect the research results too much. 

In research designs, researchers typically assess the impact of an independent variable on a dependent variable. To accurately measure the relationship, it’s important to control other variables. This is done by managing extraneous or standardized variables.

Control variables in experiments

In experiments, researchers and scientists manipulate the independent variable to understand how an independent variable influences a dependent variable. These variables are essential for maintaining the integrity of experimental outcomes, ensuring fairness, and minimizing biases induced by experimental manipulation. This practice enhances the internal validity of the study by reducing the impact of confounding variables.

Control variables in non-experimental research

In research, we sometimes cannot change the independent variable. We can use different variables to understand the connections between the main variables we are studying. 


These additional variables provide valuable insights into how the main variables interact with each other. By analyzing these relationships, we can gain a better understanding of the overall research findings. They enhance the analysis and provide deeper insight into the research dynamics.

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Why do control variables matter?

Control Variables4

It is important to control factors that could affect the results of a research project. These factors include independent and dependent variables. Understanding this is crucial for the success of the project.

Failure to control these variables could obscure the true impact of the independent variable on the outcomes. It’s hard to know if the results are from the variable or other factors, so the findings may not be trustworthy.

Control over variables is essential because even minor fluctuations in the research conditions can significantly sway the results. Moreover, regulating variables improves the coherence of the study and aids in establishing a distinct relationship between the independent and dependent variables.

To illustrate, consider an investigation into whether soil quality affects plant growth. Here, soil quality serves as the independent variable, while the rate of plant growth represents the dependent variable. Without controlling for soil quality, the validity of the study’s findings could be compromised.

Examples of control variables

Examples of elements managed in scientific inquiries are crucial for ensuring the accuracy and reliability of research findings. Consider the following scenarios:

Investigating the Impact of Soil Quality on Plant Growth:

Controlled variables include:

  • Temperature: Maintaining a consistent temperature to isolate the effect of soil quality on plant growth.
  • Amount of light: Ensuring uniform light exposure across experimental conditions.
  • Amount of water: Controlling water levels to eliminate its differences as a factor affecting plant growth.

Examining the Effect of Caffeine on Memory Recall:

Controlled variables encompass:

  • Participant age: Keeping participant age constant to isolate the impact of caffeine on memory recall.
  • Noise in the environment: Controlling environmental noise levels to prevent interference with memory recall tasks.
  • Type of memory test: Using the same memory test for everyone to see how caffeine affects memory.

Exploring Perception of Water Images in Individuals with fear of water (aquaphobia) or water aversion:

Controlled variables include:

  • Computer screen brightness: Maintaining consistent brightness levels to avoid potential effects on perception.
  • Room lighting: Ensuring uniform lighting conditions to eliminate variations in visual perception.
  • Visual stimuli sizes: Standardizing the size of water images presented to participants to isolate the influence of aquaphobia on perception.

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How do you control a variable

Various methods can achieve the control of extraneous variables in experimental, quasi-experimental, observational, and research studies.  Among them, the following approaches are particularly effective:

Random assignment method

This method proves most beneficial in experimental studies involving multiple groups. It aims to manage participant variables that may differ between groups and potentially bias the outcomes. By randomly assigning participants to different groups or conditions, this approach mitigates systematic differences, ensuring a more balanced comparison.

Standardized procedures

Ensuring uniformity in procedures among all groups or conditions is crucial for maintaining consistency. By adhering to standardized protocols, researchers can uphold uniformity throughout the experiment or study. This involves keeping all factors constant for every participant, thereby minimizing the influence of extraneous variables on the outcomes.


Experimentation entails more than just altering one factor and observing the outcome. In truth, research encompasses a multitude of influencing factors. These factors play a crucial role in maintaining stability and consistency, thereby facilitating unbiased and transparent comparisons.

In numerous experiments, even slight variations in specific factors can result in inaccuracies and biased findings. Voxco’s research toolkit empowers researchers to manage variables more effectively, enabling them to attain desired outcomes in their experiments.

  • Distinction Between Control Variable and Control Group:

It’s important to distinguish between a control variable and a control group in experimental research. While a control variable is a factor deliberately held constant, a control group serves as a comparison group that does not receive the experimental treatment.

A control group does not receive the experimental treatment. Instead, researchers compare their results to those of the group that did receive the treatment. Typically, a control group receives either no treatment, a standard treatment widely used, or a placebo (a sham treatment).

In an experimental procedure, everything besides the treatment being tested should remain consistent between the experimental and control groups

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What is a control variable?

A control variable refers to an aspect deliberately maintained constant during an experiment to facilitate the evaluation of relationships among various variables.

What is a Controlled Variable?

A controlled variable in an experiment is the one that the researcher holds constant or controls. 

It is also known as a constant or control variable. 

The constant factor is not included in the experiment. It is not an independent or dependent variable. However, a controlled variable is important because it can affect the experiment’s result.

Why is a Controlled Variable Important?

A controlled variable affects the results of an experiment, even though it is not the main focus. It serves a crucial role in ensuring the reliability and accuracy of results.

What are the examples of control variables?

When we define control variables, we can easily identify which parts of the experiment can be controlled. 

In a plant growth experiment, temperature is a control variable if it stays the same throughout the experiment. Other control variables include light, experiment duration, water amount, and plant pot size.

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