Sunday, November 29, 2009

Whats ie difference between variables and parameters?

please help



Whats ie difference between variables and parameters?microsoft net framework





Variables take on different values while parameters are constants (i.e., numbers that don't change). For example, a simple model of supply and demand might be writte:



Qd=a-bP and Qs=c+dP



The variables in this model are the quantities demanded and supplied (Qd and Qs) and the price of the good (P). The parameters in the model are the constants (a, b, c, and d).



Whats ie difference between variables and parameters?windows xp themes internet explorer



A parameter is a known constraint, whereas a variable is an unknown.
a variable represents the level of a particular population. In the mutualism section, there are two variables, x and y, which represent the two species that are helping each ot her. When we write x' or dx/dt we mean the rate of change of population x.



A parameter, on the other hand, determines how much of an effect a particular phenomenon has on the populations.
A variable is something that can be changed resulting in a different result or outcome.



A parameter is the limit to which you wish something to happen, or how you expect something to happen. Like a tolerance of + or -
Personally, I think it depends on the context. If you are talking about a statistical model, say a linear regression, I would say that model 'variables' or model parameters' are the same.



If you are looking at a simulation of some sort I think they can be different. For example, I do a lot of modeling and simulation of decision trees. The simulation will use many variables such as outcome (or path) probabilities and cost variables. To do uncertainty analysis I can actually define each variable (whether it is a path probability, cost, or whatever) by a probability distribution. Now, these distributions are based on unique parameters (e.g. a normal distribution is based on the mean and standard deviation). In this case I would consider model variables and model parameters to be different. But in my work I find it very common for people to use 'variable' and 'parameter' interchangeably no matter what the context.

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