parameter

parameter
parametric /par'euh me"trik/, parametrical, adj.
/peuh ram"i teuhr/, n.
1. Math.
a. a constant or variable term in a function that determines the specific form of the function but not its general nature, as a in f(x) = ax, where a determines only the slope of the line described by f(x).
b. one of the independent variables in a set of parametric equations.
2. Statistics. a variable entering into the mathematical form of any distribution such that the possible values of the variable correspond to different distributions.
3. Computers. a variable that must be given a specific value during the execution of a program or of a procedure within a program.
4. Usually, parameters. limits or boundaries; guidelines: the basic parameters of our foreign policy.
5. characteristic or factor; aspect; element: a useful parameter for judging long-term success.
[1650-60; < NL parametrum. See PARA-1, -METER]
Usage. 4, 5. Some object strongly to the use of PARAMETER in these newer senses. Nevertheless, the criticized uses are now well established both in educated speech and in edited writing.

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▪ mathematics and statistics
      in mathematics, a variable for which the range of possible values identifies a collection of distinct cases in a problem. Any equation expressed in terms of parameters is a parametric equation. The general equation of a straight line in slope-intercept form, y = mx + b, in which m and b are parameters, is an example of a parametric equation. When values are assigned to the parameters, such as the slope m = 2 and the y-intercept b = 3, and substitution is made, the resulting equation, y = 2x + 3, is that of a specific straight line and is no longer parametric.

      In the set of equations x = 2t + 1 and y = t2 + 2, t is called the parameter. As the parameter varies over a given domain of values, the set of solutions, or points (xy), describes a curve in the plane. The use of parameters often enables descriptions of very simple curves for which it is difficult to write down a single equation in x and y.

      In statistics, the parameter in a function is a variable whose value is sought by means of evidence from samples. The resulting assigned value is the estimate, or statistic.

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Universalium. 2010.

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