Parameter
From the Simple English Wikipedia, the free encyclopedia that anyone can change
In some non-technical contexts or in jargon, parameter may simply be a synonym for criterion.
In mathematics, statistics, and the mathematical sciences, parameters (L: auxiliary measure) are quantities that define certain relatively constant characteristics of systems or functions.
Most commonly represented θ in general form, other symbols carry standard, specific meanings. When evaluating the function over a domain or determining the response of the system over a period of time, the independent variables are modulated, while the parameters are held constant. The function or system may then be reevaluated or reprocessed with different parameters, to give a function or system with different behavior.
Loosely speaking, the term parameter is used for an argument which is intermediate in status between a variable and a constant.
[change] Example
- In a section on frequently misused words in his book The Writer's Art, James J. Kilpatrick quoted a letter from a correspondent, giving examples to illustrate the correct use of the word parameter:
| “ | W.M. Woods...a mathematician...writes... "...a variable is one of the many things a parameter is not." ... The dependent variable, the speed of the car, depends on the independent variable, the position of the gas pedal. | ” |
| “ | [Kilpatrick quoting Woods] "Now...the engineers...change the lever arms of the linkage...the speed of the car...will still depend on the pedal position...but in a...different manner. You have changed a parameter" | ” |
- If asked to imagine the graph of the relationship y = ax2, one typically visualizes a range of values of x, but only one value of a. Of course a different value of a can be used, generating a different graphical appearance. The a can therefore be considered to be a parameter: less variable than the variable x, but less constant than the constant 2.
[change] Engineering
In engineering (especially involving data acquisition) the term parameter sometimes loosely refers to an individual measured item. For example an airliner flight data recorder may record 88 different items, each termed a parameter. This usage isn't consistent, as sometimes the term channel refers to an individual measured item, with parameter referring to the setup information about that channel.
"Speaking generally, properties are those physical quantities which directly describe the physical attributes of the system; parameters are those combinations of the properties which suffice to determine the response of the system. Properties can have all sorts of dimensions, depending upon the system being considered; parameters are dimensionless, or have the dimension of time or its reciprocal." John D. Trimmer, 1950, Response of Physical Systems (New York: Wiley), p. 13.
The term can also be used in engineering contexts, however, as it is typically used in the physical sciences.
[change] See also
