Shopping on line can be easy, simple and save you lots of money. It can also take a lot of your time, frustrate you, and result in unwanted purchases. Now the same can be said for regular high street shopping, but with the vast opportunity presented by the Internet it will pay you to spend a few minutes reading this and understanding how to better optimize your Parameter shopping experience:
1. Compare - without doubt the biggest advantage that the Parameter offers shoppers today is the ability to compare thousands of Parameter at a time. This is a great thing, but not necessarily all the time! Too much can be daunting at times so take advantage of the great comparison sites and where possible let them do the hard work for you.
2. Research - if it has been said it will be on the internet. Ignorance is no longer a justifiable reason for buying the wrong thing. Take the time to research in detail everything that you could possible want to know about
3. Testimonials - don't know anybody that has bought a Parameter? Wrong! If the Parameter is good the internet will let you know. Use the Internet as a friend and get testimonials before you buy.
4. Questions - Got a question about Parameter then search the Forums, FAQ's, Blogs etc. Don't be afraid to ask .....
5. Reputation - Never heard of the company selling Parameter? Don't worry, no reason why you should know every company in the world, but you know someone that does! Use the internet to find out what people are saying about Parameter and build up a picture of their reputation for sales, returns, customer service, delivery etc.
6. Returns - still worried that even after all of the above your Parameter wont be what you want? Check out the returns policy. There is so much competition now that someone, somewhere is bound to offer the terms that you are comfortable with.
7. Feedback - happy with your Parameter then let people know, after all you are depending on others people input in your buying decision, so why not give a little back.
8. Security - check for the yellow padlock on the Parameter site before you buy, and the s after http:/ /i.e. https:// = a secure site
9. Contact - got a question about Parameter, or want to leave a comment then check out the sites contact page. Reputable companies have them and respond.
10. Payment - ready to pay for your Parameter, then use your credit card or PayPal! Be aware of companies that don't accept them, there may be genuine reasons but given the huge amount of choice you have when buying online there is no reason at all not to buy via credit card or PayPal.
Parameters, in the plural form, has recently become popular with non-technical users to mean limits, but this should not be confused with the word's technical meaning.
In
mathematics,
statistics, and the mathematical sciences,
parameters (Latin
auxiliary measure) are quantities that define certain relatively constant characteristics of systems or mathematical functions. Often represented by 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 varied, 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.
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:
- A equalization is an audio filter that allows the frequency of maximum cut or boost to be set by one control, and the size of the cut or boost by another. These settings, the frequency level of the peak or trough, are two of the parameters of a frequency response curve, and in a two-control equaliser they completely describe the curve. More elaborate parametric equalisers may allow other parameters to be varied, such as skew. These parameters each describe some aspect of the response curve seen as a whole, over all frequencies. A equalization provides individual level controls for various frequency bands, each of which acts only on that particular frequency band.
- If asked to imagine the graph of the relationship y= a x^2, 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.
Parameters in various contexts in math and science
Mathematical functions
Mathematical functions typically can have one or more variables and zero or more parameters. The two are often distinguished by being grouped separately in the list of Argument#Mathematics, science and linguistics that the function takes:
f(x_1, x_2, \dots; a_1, a_2, \dots) = \cdots\,
The symbols before the semicolon in the function's definition, in this example the x's, denote variables, while those after it, in this example the a's, denote parameters.
Strictly speaking, parameters are denoted by the symbols that are part of the function's
definition, while arguments are the values that are supplied to the function when it is used. Thus, a parameter might be something like "the ratio of the cylinder's radius to its height", while the argument would be something like "2" or "0.1".
In some informal situations people regard it as a matter of convention (and therefore a historical accident) whether some or all the arguments of a function are called parameters.
Analytic geometry
In
analytic geometry, curves are often given as the image of some function. The argument of the function is invariably called "the parameter". A circle of radius 1 centered at the origin can be specified in more than one form:
x^2+y^2=1
(x,y)=(\cos t,\sin t)
where
t is the
parameter.
A somewhat more detailed description can be found at parametric equation.
Mathematical analysis
In
mathematical analysis, one often considers "integrals dependent on a parameter". These are of the form
F(t)=\int_{x_0(t)}^{x_1(t)}f(x;t)\,dx.
In this formula,
t is on the left-hand side the argument of the function
F, and it is on the right-hand side the
parameter that the integral depends on. When evaluating the integral,
t is held constant, and so it considered a parameter. If we are interested in the value of
F for different values of
t, then, we now consider it to be a variable. The quantity
x is a
dummy variable or
variable of integration (confusingly, also sometimes called a
parameter of integration).
Probability theory
In
probability theory, one may describe the
probability distribution of a
random variable as belonging to a
family of probability distributions, distinguished from each other by the values of a finite number of
parameters. For example, one talks about "a
Poisson distribution with mean value λ". The function defining the distribution (the
probability mass function) is:
f(k;\lambda)=\frac{e^{-\lambda} \lambda^k}{k!}.
This example nicely illustrates the distinction between constants, parameters, and variables.
e is Euler's Number, a fundamental mathematical constant. The parameter λ is the mean number of observations of some phenomenon in question, a property characteristic of the system.
k is a variable, in this case the number of occurrences of the phenomenon actually observed from a particular sample. If we want to know the probability of observing
k1 occurrences, we plug it into the function to get f(k_1 ; \lambda). Without altering the system, we can take multiple samples, which will have a range of values of
k, but the system will always be characterized by the same λ.
For instance, suppose we have a radioactivity sample that emits, on average, five particles every ten minutes. We take measurements of how many particles the sample emits over ten-minute periods. The measurements will exhibit different values of
k, and if the sample behaves according to Poisson statistics, then each value of
k will come up in a proportion given by the probability mass function above. From measurement to measurement, however, λ remains constant at 5. If we do not alter the system, then the parameter λ is unchanged from measurement to measurement; if, on the other hand, we modulate the system by replacing the sample with a more radioactive one, then the parameter λ would increase.
Another common distribution is the normal distribution, which has as parameters the mean μ and the variance σ2.
It is possible to use the sequence of
moment (mathematics) (mean, mean square, ...) or
cumulants (mean, variance, ...) as parameters for a probability distribution.
Statistics and econometrics
In
statistics and
econometrics, the probability framework above still holds, but attention shifts to statistical estimation the parameters of a distribution based on observed data, or
Hypothesis testing about them. In
classical statistics these parameters are considered "fixed but unknown", but in
Bayesian probability they are random variables with distributions of their own.
It is possible to make statistical inferences without assuming a particular
parametric family of probability distributions. In that case, one speaks of non-parametric statistics as opposed to the
parametric statistics described in the previous paragraph. For example, Spearman's rank correlation coefficient is a non-parametric test as it is computed from the order of the data regardless of the actual values, whereas
Pearson product-moment correlation coefficient is a parametric test as it is computed directly from the data and can be used to derive a mathematical relationship.
Statistics are mathematical characteristics of samples which can be used as estimates of parameters, mathematical characteristics of the populations from which the samples are drawn. For example, the
sample mean (\overline X) can be used as an estimate of the
mean parameter (μ) of the population from which the sample was drawn.
Other fields
Other fields use the term "parameter" as well, but with a different meaning.
Logic
In logic, the parameters passed to (or operated on by) an
open predicate are called
parameters by some authors (e.g., Dag Prawitz, "Natural Deduction"; Paulson, "Designing a theorem prover"). Parameters locally defined within the predicate are called
variables. This extra distinction pays off when defining substitution (without this distinction special provision has to be made to avoid variable capture). Others (maybe most) just call parameters passed to (or operated on by) an open predicate
variables, and when defining substitution have to distinguish between
free variables and
bound variables.
===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.
Computer science
When the terms
formal parameter and
actual parameter are used, they generally correspond with the
parameter (computer science). In the definition of a function such as
f(
x) =
x + 2,
x is a
formal parameter. When the function is used as in
y =
f(3) + 5 or just the value of
f(3),
3 is the
actual parameter value that is used to solve the equation. These concepts are discussed in a more precise way in
functional programming and its foundational disciplines,
lambda calculus and combinatory logic.
In computing, the values passed to a function subroutine are more normally called
arguments.
See also
- Parametrization (i.e., coordinate system)
- Parametrization (climate)
- Parsimony (with regards to the trade-off of many or few parameters in data fitting)
Parameters, in the plural form, has recently become popular with non-technical users to mean limits, but this should not be confused with the word's technical meaning.
In
mathematics, statistics, and the mathematical
sciences,
parameters (Latin
auxiliary measure) are quantities that define certain relatively constant characteristics of systems or mathematical functions. Often represented by 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 varied, 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.
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:
- A equalization is an audio filter that allows the frequency of maximum cut or boost to be set by one control, and the size of the cut or boost by another. These settings, the frequency level of the peak or trough, are two of the parameters of a frequency response curve, and in a two-control equaliser they completely describe the curve. More elaborate parametric equalisers may allow other parameters to be varied, such as skew. These parameters each describe some aspect of the response curve seen as a whole, over all frequencies. A equalization provides individual level controls for various frequency bands, each of which acts only on that particular frequency band.
- If asked to imagine the graph of the relationship y= a x^2, 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.
Parameters in various contexts in math and science
Mathematical functions
Mathematical functions typically can have one or more variables and zero or more parameters. The two are often distinguished by being grouped separately in the list of Argument#Mathematics, science and linguistics that the function takes:
f(x_1, x_2, \dots; a_1, a_2, \dots) = \cdots\,
The symbols before the semicolon in the function's definition, in this example the x's, denote variables, while those after it, in this example the a's, denote parameters.
Strictly speaking, parameters are denoted by the symbols that are part of the function's
definition, while arguments are the values that are supplied to the function when it is used. Thus, a parameter might be something like "the ratio of the cylinder's radius to its height", while the argument would be something like "2" or "0.1".
In some informal situations people regard it as a matter of convention (and therefore a historical accident) whether some or all the arguments of a function are called parameters.
Analytic geometry
In
analytic geometry, curves are often given as the image of some function. The argument of the function is invariably called "the parameter". A circle of radius 1 centered at the origin can be specified in more than one form:
x^2+y^2=1
(x,y)=(\cos t,\sin t)
where
t is the
parameter.
A somewhat more detailed description can be found at parametric equation.
Mathematical analysis
In
mathematical analysis, one often considers "integrals dependent on a parameter". These are of the form
F(t)=\int_{x_0(t)}^{x_1(t)}f(x;t)\,dx.
In this formula,
t is on the left-hand side the argument of the function
F, and it is on the right-hand side the
parameter that the integral depends on. When evaluating the integral,
t is held constant, and so it considered a parameter. If we are interested in the value of
F for different values of
t, then, we now consider it to be a variable. The quantity
x is a
dummy variable or
variable of integration (confusingly, also sometimes called a
parameter of integration).
Probability theory
In probability theory, one may describe the
probability distribution of a
random variable as belonging to a
family of probability distributions, distinguished from each other by the values of a finite number of
parameters. For example, one talks about "a
Poisson distribution with mean value λ". The function defining the distribution (the probability mass function) is:
f(k;\lambda)=\frac{e^{-\lambda} \lambda^k}{k!}.
This example nicely illustrates the distinction between constants, parameters, and variables.
e is Euler's Number, a fundamental mathematical constant. The parameter λ is the
mean number of observations of some phenomenon in question, a property characteristic of the system.
k is a variable, in this case the number of occurrences of the phenomenon actually observed from a particular sample. If we want to know the probability of observing
k1 occurrences, we plug it into the function to get f(k_1 ; \lambda). Without altering the system, we can take multiple samples, which will have a range of values of
k, but the system will always be characterized by the same λ.
For instance, suppose we have a
radioactivity sample that emits, on average, five particles every ten minutes. We take measurements of how many particles the sample emits over ten-minute periods. The measurements will exhibit different values of
k, and if the sample behaves according to Poisson statistics, then each value of
k will come up in a proportion given by the probability mass function above. From measurement to measurement, however, λ remains constant at 5. If we do not alter the system, then the parameter λ is unchanged from measurement to measurement; if, on the other hand, we modulate the system by replacing the sample with a more radioactive one, then the parameter λ would increase.
Another common distribution is the
normal distribution, which has as parameters the mean μ and the variance σ2.
It is possible to use the sequence of
moment (mathematics) (mean, mean square, ...) or
cumulants (mean, variance, ...) as parameters for a probability distribution.
Statistics and econometrics
In statistics and
econometrics, the probability framework above still holds, but attention shifts to statistical estimation the parameters of a distribution based on observed data, or
Hypothesis testing about them. In classical statistics these parameters are considered "fixed but unknown", but in Bayesian probability they are random variables with distributions of their own.
It is possible to make statistical inferences without assuming a particular
parametric family of probability distributions. In that case, one speaks of
non-parametric statistics as opposed to the
parametric statistics described in the previous paragraph. For example,
Spearman's rank correlation coefficient is a non-parametric test as it is computed from the order of the data regardless of the actual values, whereas Pearson product-moment correlation coefficient is a parametric test as it is computed directly from the data and can be used to derive a mathematical relationship.
Statistics are mathematical characteristics of samples which can be used as estimates of parameters, mathematical characteristics of the populations from which the samples are drawn. For example, the
sample mean (\overline X) can be used as an estimate of the
mean parameter (μ) of the population from which the sample was drawn.
Other fields
Other fields use the term "parameter" as well, but with a different meaning.
Logic
In
logic, the parameters passed to (or operated on by) an
open predicate are called
parameters by some authors (e.g., Dag Prawitz, "Natural Deduction"; Paulson, "Designing a theorem prover"). Parameters locally defined within the predicate are called
variables. This extra distinction pays off when defining substitution (without this distinction special provision has to be made to avoid variable capture). Others (maybe most) just call parameters passed to (or operated on by) an open predicate
variables, and when defining substitution have to distinguish between
free variables and
bound variables.
===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.
Computer science
When the terms
formal parameter and
actual parameter are used, they generally correspond with the
parameter (computer science). In the definition of a function such as
f(
x) =
x + 2,
x is a
formal parameter. When the function is used as in
y =
f(3) + 5 or just the value of
f(3),
3 is the
actual parameter value that is used to solve the equation. These concepts are discussed in a more precise way in
functional programming and its foundational disciplines, lambda calculus and
combinatory logic.
In
computing, the values passed to a function subroutine are more normally called
arguments.
See also
- Parametrization (i.e., coordinate system)
- Parametrization (climate)
- Parsimony (with regards to the trade-off of many or few parameters in data fitting)
Parameter Magazine
news. Bruce New: New artist in the gallery. Click the picture or read more here. * * * The Other Room: An evening of innovative poetry at The Old Abbey Inn, Manchester ...
parameter RAM from FOLDOC
parameter RAM (PRAM) A small memory in a Macintosh with a battery power supply which stores system parameters (desktop pattern, selectable memory configuration, etc.) when the ...
Parameter - Wikipedia, the free encyclopedia
In mathematics, statistics, and the mathematical sciences, a parameter (G: auxiliary measure) is a quantity that defines certain characteristics of systems or functions.
Parameter (computer science) - Wikipedia, the free encyclopedia
In computer programming, a parameter is a variable which takes on the meaning of a corresponding argument passed in a call to a subroutine. In the most common case, call-by-value ...
Multi parameter sensors
The Greenspan multi-parameter range of sensors provides a choice of combinations of water quality and level parameters to meet the majority of environmental monitoring requirements
single parameter sensors
Greenspan Analytical's range of single parameter water quality sensors are available in a wide variety of configurations to meet the diverse demands of monitoring sites.
The British Oceanographic Data Centre (BODC) Parameter Dictionary for ...
The British Oceanographic Data Centre (BODC) Parameter Dictionary contains entries for almost 19,000 physical, chemical, biological and geological parameter codes for marine data.
Parameter AB: imaging, optronics, nano- and micropositioning
Parameter AB is a distributor on the Nordic market of high-technology content miniature components for flow control, micro- and nano-positioning as well as components and subsystem ...
Parameter
About Parameter ... Back to Statistics Contents] A parameter is a measurement on a population that characterizes one of its features.
Add / Edit Parameter
Add / Edit Parameter Add Parameter. Adds a parameter to the Add Query Parmeter List. Name. Assign a parameter name. A parameter name cannot contain spaces.
