Independent and Dependent Variables

Fundamentals of Social Statistics by Adam J. McKee

In scientific experiments, researchers study two main types of variables. The independent variable is the one that the researcher changes or manipulates. The dependent variable is what the researcher observes to see if it changes as a result of the independent variable.

Understanding the Independent Variable

When scientists conduct an experiment, they usually have a question in mind. To answer this question, they need to make changes to one thing and observe what happens to another. The thing they change is the independent variable.

For example, let’s say a researcher wants to know if different amounts of sunlight affect plant growth. In this case, the independent variable is the amount of sunlight the plants receive. The researcher might put some plants in a room with a lot of sunlight and some in a room with less. By changing the amount of sunlight, the researcher aims to find out how it affects plant growth.

The Role of the Dependent Variable

The dependent variable is what you measure in the experiment. It’s what you’re curious to learn about. In our plant experiment, the dependent variable is the growth of the plants. The researcher measures how tall the plants grow under different light conditions.

The term “dependent” is used because this variable depends on the independent variable. If the plants grow more with more sunlight, that growth is dependent on the amount of sunlight they received.

The Importance of a Control Group

In any well-designed experiment, a control group is essential. This group serves as a standard to compare the experimental group to. The control group doesn’t receive the treatment or the change in the independent variable.

For example, in the plant experiment, the control group would be plants kept in a room with a normal amount of sunlight. These plants aren’t exposed to the extra sunlight or the lesser amount. By comparing the growth of plants in the control group with those in the experimental groups, the researcher can more confidently say whether the change in sunlight made a difference.

How the Variables Interact

The independent and dependent variables have a special relationship. The purpose of the experiment is to find out whether a change in the independent variable causes a change in the dependent variable.

In the plant example, the question is: Does changing the amount of sunlight (independent variable) cause the plants to grow more or less (dependent variable)? If the plants in the sunnier room grow taller than those in the control group, then the researcher may conclude that more sunlight boosts plant growth.

The Core of Scientific Inquiry

Understanding the independent and dependent variables is crucial for scientific research. This understanding allows scientists to design experiments that can answer specific questions. By carefully manipulating one thing (the independent variable) and observing its effect on another (the dependent variable), they can draw meaningful conclusions.


In an experiment, the independent variable is what the researcher changes to see its impact. The dependent variable is what the researcher measures to see if it changes because of the independent variable. Including a control group adds validity to the experiment by offering a basis for comparison. These variables are the building blocks of scientific research, helping us understand the world around us.

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Last Modified:  09/11/2023

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