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  2. Population density - Wikipedia

    en.wikipedia.org/wiki/Population_density

    Population density is the number of people per unit of area, usually transcribed as "per square kilometer" or square mile, and which may include or exclude, for example, areas of water or glaciers. Commonly this is calculated for a county, city, country, another territory or the entire world . The world's population is around 8,000,000,000 [3 ...

  3. Urban density - Wikipedia

    en.wikipedia.org/wiki/Urban_density

    Urban density is a term used in urban planning and urban design to refer to the number of people inhabiting a given urbanized area. As such it is to be distinguished from other measures of population density. Urban density is considered an important factor in understanding how cities function. Research related to urban density occurs across ...

  4. Number density - Wikipedia

    en.wikipedia.org/wiki/Number_density

    Number density. The number density (symbol: n or ρN) is an intensive quantity used to describe the degree of concentration of countable objects ( particles, molecules, phonons, cells, galaxies, etc.) in physical space: three-dimensional volumetric number density, two-dimensional areal number density, or one-dimensional linear number density.

  5. Density matrix - Wikipedia

    en.wikipedia.org/wiki/Density_matrix

    In quantum mechanics, a density matrix (or density operator) is a matrix that describes the quantum state of a physical system. It allows for the calculation of the probabilities of the outcomes of any measurement performed upon this system, using the Born rule. It is a generalization of the more usual state vectors or wavefunctions: while ...

  6. Rate of natural increase - Wikipedia

    en.wikipedia.org/wiki/Rate_of_natural_increase

    Data unavailable. In Demography, the rate of natural increase ( RNI ), also known as natural population change, is defined as the birth rate minus the death rate of a particular population, over a particular time period. [1] It is typically expressed either as a number per 1,000 individuals in the population [2] or as a percentage. [3]

  7. Likelihood function - Wikipedia

    en.wikipedia.org/wiki/Likelihood_function

    t. e. The likelihood function (often simply called the likelihood) is the joint probability mass (or probability density) of observed data viewed as a function of the parameters of a statistical model. [1] [2] [3] Intuitively, the likelihood function is the probability of observing data assuming is the actual parameter.

  8. Population dynamics - Wikipedia

    en.wikipedia.org/wiki/Population_dynamics

    The half-life of a population is the time taken for the population to decline to half its size. We can calculate the half-life of a geometric population using the equation: N t = λ t N 0 by exploiting our knowledge of the fact that the population (N) is half its size (0.5N) after a half-life.

  9. Density estimation - Wikipedia

    en.wikipedia.org/wiki/Density_Estimation

    In statistics, kernel density estimation (KDE) is the application of kernel smoothing for probability density estimation, i.e., a non-parametric method to estimate the probability density function of a random variable based on kernels as weights. KDE answers a fundamental data smoothing problem where inferences about the population are made ...