What Is the Difference Between a Control & a Controlled Variable?

By Jade Blue; Updated April 25, 2017
Controls and controlled variables are key elements in a good experimental setup.

What is the difference between a control and a controlled variable? It is the equivalent of looking at the entire setup, versus one piece of the puzzle. A control helps scientists observe changes within an experiment. Control variables are components that remain the same, despite additional changes made within the experiment.

Understand

What is the difference between a control and a controlled variable? According to the dictionary, a control checks or corrects information obtained in other experiments by removing all variables, except the one of interest to the researcher. There are three types of variables: independent, dependent and controlled. Control variables are items or scenarios that remain present throughout the experiment. They are meant to establish or refute relationships between dependent and independent variables. When water flows through a sink faucet, the independent variable is how much the tap is opened. Dependent variables are the resulting amount of water flow. Controlled variables are the faucet and water pressure, as long they remain unadjusted.

Setup

Controls normally require no manipulation on the part of the research team. When the effects of an automotive wax were being monitored, no product was applied to the control area in order to create a stark contrast between treated and non-treated areas. Controlled variables require a degree of maintenance to ensure all factors remain the same throughout the course of an experiment.

Numbers

Experiments only need one control, while it is common to find more than one controlled variable within an experiment. When mice are placed in bell jars, the species of the mouse and the jar in which it was placed remain consistent, making them controlled variables. When additional items are placed in different jars, results are compared with the control jar that contains just a mouse.

Impact

While controls give researchers an indication of changes that have occurred within an experiment, courtesy of dependent and independent variables, control variables give validity to all acquired information. If any aspect of a controlled variable is altered, it creates unreliable results. The difference between a control and a controlled variable may be slight, but they are both essential in experimental research.

About the Author

Splitting her time between El Paso, Texas and Philadelphia, Penn., Jade Blue began writing in 2009. Blue has written for various websites, specializing in travel-related topics. She holds a Bachelor of Science in psychology from Philadelphia University.