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Encyclopedia > Independent variable

In an experimental design, the independent variable (argument of a function, also called a predictor variable) is the variable that is manipulated or selected by the experimenter to determine its relationship to an observed phenomenon (the dependent variable). In such an experiment, an attempt is made to find evidence that the values of the independent variable determine the values of the dependent variable (that which is being measured). The independent variable can be changed as required, and its values do not represent a problem requiring explanation in an analysis, but are taken simply as given. Image File history File links Broom_icon. ... The first statistician to consider a methodology for the design of experiments was Sir Ronald A. Fisher. ... In computer science and mathematics, a variable (IPA pronunciation: ) (sometimes called a pronumeral) is a symbolic representation denoting a quantity or expression. ... Observation is an activity of a sapient or sentient living being, which senses and assimiliates the knowledge of a phenomenon in its framework of previous knowledge and ideas. ... In experimental design, a dependent variable (also known as response variable, responding variable or regressand) is a factor whose values in different treatment conditions are compared. ...


More generally, the independent variable is the thing that one actively controls/changes, while the dependent variable is the thing that changes as a result. In other words, the independent variable is the “presumed cause”, while the dependent variable is the “presumed effect” of the independent variable. In experimental design, a dependent variable (also known as response variable, responding variable or regressand) is a factor whose values in different treatment conditions are compared. ...


The independent variable is also called the manipulated variable, predictor variable or exposure variable.

Contents

Mathematics usage

When graphing a set of collected data, the independent variable is graphed on the x-axis (see Cartesian coordinates). In mathematics, and functional analysis in particular, it was traditional to define the set of independent variables as the only set of variables in a given context that can be altered. For, even though any function defines a bilateral relation between variables, and it’s even true that two variables might be connected by an implicit equation (for instance, cf. the definition of a circle, , when computing derivatives it is nonetheless necessary to take a group of variables as “independent”, or else the derivative has no meaning). Cartesian means relating to the French mathematician and philosopher Descartes, who, among other things, worked to merge algebra and Euclidean geometry. ... Euclid, Greek mathematician, 3rd century BC, as imagined by by Raphael in this detail from The School of Athens. ... Functional analysis is the branch of mathematics, and specifically of analysis, concerned with the study of spaces of functions. ...


Advertising usage

An independent variable is what you know about the customer, or what you can't observe.


Examples

In a study of how different dosages of a drug are related to the severity of symptoms of a disease, a researcher could compare the frequency and intensity of varying symptoms (the dependent variables) when varying dosages (the independent variable) are administered, and attempt to draw a conclusion. Dosage is Collective Souls fourth studio album, released on February 9, 1999. ... Oral medication A medication is a licenced drug taken to cure or reduce symptoms of an illness or medical condition. ... The term symptom (from the Greek syn = con/plus and pipto = fall, together meaning co-exist) has two similar meanings in the context of physical and mental health: Strictly, a symptom is a sensation or change in health function experienced by a patient. ... It has been suggested that Refractory disease be merged into this article or section. ...


In measuring the acceleration of a vehicle, time is usually the independent variable and speed is the dependent variable. This is because when taking measurements, times are usually predetermined, and the resulting speed of the vehicle is recorded at those times. As far as the experiment is concerned, the speed is dependent on the time. Since the decision is made to measure the speed at certain times, time is the independent variable.


See also


  Results from FactBites:
 
independent variable: Definition and Much More from Answers.com (798 words)
In an experimental design, the independent variable (also called the explanatory variable or manipulated variable) is the variable which is manipulated or selected by the experimenter to determine its relationship to an observed phenomenon (the dependent variable).
Often the independent variable is time, which is allowed to change, or a physical quantity (such as voltage, force or frequency) that can be accurately adjusted.
To visualise the effect of the independent variable on the dependent variable, a line chart is commonly used.
variable: Information from Answers.com (2553 words)
Variables are generally distinct from parameters, although what is a variable in one context may be a parameter in another.
Variables are often represented by letters of the Roman alphabet, but are also represented by letters of other alphabets, such as the Greek alphabet, as well as various other symbols.
By contrast, it is permissible for a variable binding to extend beyond its scope, as occurs in Lisp closures and C static variables.
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