Controlling for a variable

# Controlling for a variable

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Encyclopedia
Controlling for a variable refers to the deliberate varying of the experiment
Experiment
An experiment is a methodical procedure carried out with the goal of verifying, falsifying, or establishing the validity of a hypothesis. Experiments vary greatly in their goal and scale, but always rely on repeatable procedure and logical analysis of the results...

al conditions in order to see the impact of a specific variable
Variable (mathematics)
In mathematics, a variable is a value that may change within the scope of a given problem or set of operations. In contrast, a constant is a value that remains unchanged, though often unknown or undetermined. The concepts of constants and variables are fundamental to many areas of mathematics and...

when predicting the outcome variable (see independent and dependent variables). Controlling tends to reduce the experimental error
Errors and residuals in statistics
In statistics and optimization, statistical errors and residuals are two closely related and easily confused measures of the deviation of a sample from its "theoretical value"...

. A control is something that does not change in the experiment.

Controlling for a variable is also a term used in statistical data analysis
Statistics
Statistics is the study of the collection, organization, analysis, and interpretation of data. It deals with all aspects of this, including the planning of data collection in terms of the design of surveys and experiments....

when inferences may need to be made for the relationships within one set of variables given that some of the inter-relations may derive from relations to variables in another set. This is broadly equivalent to conditioning on the variables in the second set, although only linear relations may be taken into account. Such analyses may be described as "controlling for variable X", or "controlling for the variations in X".