variable

In the context of scientific experiments, a variable is any factor that could change or be changed.

So, for instance, if you’re measuring how effective a medication is, variables could include the amount of dosage, how frequently it’s taken, and the characteristics of each test subject, such as their age and weight. In general, variables are called variables because they vary. However, in scientific experiments, some variables are kept the same on purpose—such a variable is called a control variable (or sometimes simply just a control).

There are three different types of variables: dependent variables, independent variables, and control variables. Independent variables are the factors that you change. Dependent variables are things that are affected by the changes that you make—the results of the tests (which depend on the independent variables). Control variables are the factors that you do not change. They are kept the same for every test or measurement in order to make sure that the results can be compared fairly.

For example, let’s say you’re trying to figure out which brand of plant food will help a sunflower grow to the tallest height. The dependent variable is the final height of the sunflower. The independent variable (the factor that you change) is the brand of plant food. There are a number of other factors that could impact the growth of the plant, including things like the amount of sunlight and the amount of water. To allow for a proper comparison of the results, these need to be control variables—they need to be controlled, or kept the same. This way, you can have a greater degree of certainty that the final difference in heights (the dependent variable) is due to which food each sunflower received (the independent variable), not differences in sunlight or water.

Properly setting the variables is crucial to scientifically sound experiments and studies.

Science is messy. We like to think of experimentation as a simple process of “change one thing and record what happens,” but in reality, every possible subject of study has dozens of different factors that can impact the results—the variables.

Scientists are trained to be careful when setting all the variables for an experiment. In many experiments, even minor unintended fluctuations in some factor can make the findings inaccurate or misleading. The results of experiments are sometimes later debunked after it has been revealed that variables somehow skewed the results.

Understanding the importance of variables will make you more likely to draw sound conclusions and less likely to fall for claims based on faulty science. For example, when examining suspicious statistics or experiment results, a good place to start is to ask what variables were involved, including whether control variables were used and what they were. Knowing the variables is crucial to critical thinking.

The term variable is used in the context of formal scientific experiments, but you use the same concept all the time without thinking about it. The process of trial and error involves trying new methods of doing something until you get the results you want. The new methods are the independent variables and the results of each attempt are the dependent variables.

Dependent, independent, and control variables are crucial elements of any experiment, regardless of what is being studied.

Students experiment with different-material balls (independent variable) and same dropping distance (control variable), to determine height of the bounce (dependent variable). Good work, 6White Science students. @cjhdragons #d26embracethejourney pic.twitter.com/1QBWjD0aQS

— Sarah Edwards, BS, MA (@safetysarah11) October 1, 2019

• dependent variable
• independent variable
• control variable
• experiment
• scientific method

True or False? 

In an experiment, the control variable is the one that you change.