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Quantities can be used as being infinitesimal, arguments of a function, variables in an expression (independent or dependent), or probabilistic as in random and stochastic quantities. In mathematics, magnitudes and multitudes are also not only two distinct kinds of quantity but furthermore relatable to each other.
The most familiar measure of dependence between two quantities is the Pearson product-moment correlation coefficient (PPMCC), or "Pearson's correlation coefficient", commonly called simply "the correlation coefficient". It is obtained by taking the ratio of the covariance of the two variables in question of our numerical dataset, normalized to ...
Conjugate variables are pairs of variables mathematically defined in such a way that they become Fourier transform duals, [1] [2] or more generally are related through Pontryagin duality. The duality relations lead naturally to an uncertainty relation—in physics called the Heisenberg uncertainty principle —between them.
An extensive property is a physical quantity whose value is proportional to the size of the system it describes, [8] or to the quantity of matter in the system. For example, the mass of a sample is an extensive quantity; it depends on the amount of substance. The related intensive quantity is the density which is independent of the amount.
The measurable variables in economics are quantity, quality and distribution. Measuring quantity in economics follows the rules of measuring in physics. Quality as a variable refers to qualitative changes in the production process. Qualitative changes take place when relative of different constant-price input and output factors alter.
In mathematics, a rate is the quotient of two quantities, often represented as a fraction. [1] If the divisor (or fraction denominator) in the rate is equal to one expressed as a single unit, and if it is assumed that this quantity can be changed systematically (i.e., is an independent variable), then the dividend (the fraction numerator) of the rate expresses the corresponding rate of change ...
[a] In this sense, some common independent variables are time, space, density, mass, fluid flow rate, [1] [2] and previous values of some observed value of interest (e.g. human population size) to predict future values (the dependent variable). [3] Of the two, it is always the dependent variable whose variation is being studied, by altering ...
where σ ij represents the covariance of two variables x i and x j. The double sum is taken over all combinations of i and j, with the understanding that the covariance of a variable with itself is the variance of that variable, that is, σ ii = σ i 2. Also, the covariances are symmetric, so that σ ij = σ ji. Again, as was the case with the ...