What Is the Difference Between a Control Variable and Control Group?

Control Group Versus Control Variable in an Experiment

There are different types of 'controls' in an experiment.
There are different types of 'controls' in an experiment. Cultura Science/Matt Lincoln / Getty Images

 In experiments, controls are factors that you hold constant or don't expose to the condition you are testing. Although control variables and the control group are the same in this respect, the terms refer to two different things.

A control variable is any factor you control or hold constant during an experiment. A control variable is also called a controlled variable or constant variable.

Control Variable Example: If you are studying the effect of the amount of water on seed germination, control variables might include temperature, light, and type of seed.

In contrast, there may be variables you can't easily control, such as humidity, noise, vibration, magnetic fields.

Ideally, a researcher wants to control every variable, but this isn't always possible. It's a good idea to note all recognizable variables in a lab notebook for reference.

A control group is a set of experimental samples or subjects that are kept separate and aren't exposed to the independent variable.

Control Group Example: In an experiment to determine whether zinc helps people recover faster from a cold, the experimental group would be people taking zinc, while the control group would be people taking a placebo (not exposed to extra zinc, the independent variable).

A controlled experiment is one in which every parameter is held constant except for the experimental (independent) variable. Usually, controlled experiments have control groups. Sometimes a controlled experiment compares a variable against a standard.

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Helmenstine, Anne Marie, Ph.D. "What Is the Difference Between a Control Variable and Control Group?" ThoughtCo, Mar. 6, 2017, thoughtco.com/difference-between-control-variable-and-group-609102. Helmenstine, Anne Marie, Ph.D. (2017, March 6). What Is the Difference Between a Control Variable and Control Group? Retrieved from https://www.thoughtco.com/difference-between-control-variable-and-group-609102 Helmenstine, Anne Marie, Ph.D. "What Is the Difference Between a Control Variable and Control Group?" ThoughtCo. https://www.thoughtco.com/difference-between-control-variable-and-group-609102 (accessed November 23, 2017).