What is the difference between controlled and independent variables

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She has taught science courses at the high school, college, and graduate levels. Facebook Facebook Twitter Twitter. Featured Video. Cite this Article Format. Helmenstine, Anne Marie, Ph. Independent Variable Definition and Examples. Understanding Simple vs Controlled Experiments. Dependent Variable Definition and Examples. Todd Helmenstine is a science writer and illustrator who has taught physics and math at the college level.

He holds bachelor's degrees in both physics and mathematics. Updated October 07, Featured Video. Cite this Article Format. Helmenstine, Todd. Independent Variable Definition and Examples. Dependent Variable Definition and Examples. What Are Independent and Dependent Variables? Understanding Simple vs Controlled Experiments. How Intervening Variables Work in Sociology. Null Hypothesis Definition and Examples.

Uncontrolled variables are alternative explanations for your results. In an experiment , a researcher is interested in understanding the effect of an independent variable on a dependent variable. Control variables help you ensure that your results are solely caused by your experimental manipulation.

The independent variable is whether the vitamin D supplement is added to a diet, and the dependent variable is the level of alertness. To make sure any change in alertness is caused by the vitamin D supplement and not by other factors, you control these variables that might affect alertness:. Instead, control variables are measured and taken into account to infer relationships between the main variables of interest. To account for other factors that are likely to influence the results, you also measure these control variables:.

There are several ways to control extraneous variables in experimental designs, and some of these can also be used in observational or quasi-experimental designs. In experimental studies with multiple groups, participants should be randomly assigned to the different conditions.

Random assignment helps you balance the characteristics of groups so that there are no systematic differences between them. This method of assignment controls participant variables that might otherwise differ between groups and skew your results. To make sure that participant characteristics have no effect on the study, participants are randomly assigned to one of two groups: a control group or an experimental group.

The groups should only differ in the independent variable manipulation so that you can isolate its effect on the dependent variable the results.

To control variables, you can hold them constant at a fixed level using a protocol that you design and use for all participant sessions. For example, the instructions and time spent on an experimental task should be the same for all participants in a laboratory setting. You will choose different light colors like green, red, yellow, etc. You are not measuring the light. A dependent variable is the measurement that changes in response to what you changed in the experiment.

This variable is dependent on other variables; hence the name! For example, in the plant growth experiment, the dependent variable would be plant growth. You could measure this by measuring how much the plant grows every two days. You could also measure it by measuring the rate of photosynthesis. Either of these measurements are dependent upon the kind of light you give the plant.

A control variable in science is any other parameter affecting your experiment that you try to keep the same across all conditions. For example, one control variable in the plant growth experiment could be temperature. You want to measure only the effect of light, not temperature. For this reason you would want to keep the temperature the same across all of your plants.

In other words, you would want to control the temperature. Another example is the amount of water you give the plant.