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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. Probability density function - Wikipedia

    en.wikipedia.org/wiki/Probability_density_function

    In the field of statistical physics, a non-formal reformulation of the relation above between the derivative of the cumulative distribution function and the probability density function is generally used as the definition of the probability density function. This alternate definition is the following:

  4. Likelihood function - Wikipedia

    en.wikipedia.org/wiki/Likelihood_function

    In frequentist statistics, the likelihood function is itself a statistic that summarizes a single sample from a population, whose calculated value depends on a choice of several parameters θ 1... θ p, where p is the count of parameters in some already-selected statistical model. The value of the likelihood serves as a figure of merit for the ...

  5. Normal distribution - Wikipedia

    en.wikipedia.org/wiki/Normal_distribution

    The split normal distribution is most directly defined in terms of joining scaled sections of the density functions of different normal distributions and rescaling the density to integrate to one. The truncated normal distribution results from rescaling a section of a single density function. Infinite divisibility and Cramér's theorem

  6. Quantile - Wikipedia

    en.wikipedia.org/wiki/Quantile

    Quantile. (−∞,Q) (Q,Q) (Q,Q) (Q,+∞) In statistics and probability, quantiles are cut points dividing the range of a probability distribution into continuous intervals with equal probabilities, or dividing the observations in a sample in the same way. There is one fewer quantile than the number of groups created.

  7. Probability distribution - Wikipedia

    en.wikipedia.org/wiki/Probability_distribution

    This is the definition of a probability density function, so that absolutely continuous probability distributions are exactly those with a probability density function. In particular, the probability for X {\displaystyle X} to take any single value a {\displaystyle a} (that is, a ≤ X ≤ a {\displaystyle a\leq X\leq a} ) is zero, because an ...

  8. 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 ...

  9. Demographic statistics - Wikipedia

    en.wikipedia.org/wiki/Demographic_statistics

    Demographic statistics are measures of the characteristics of, or changes to, a population. Records of births, deaths, marriages, immigration and emigration and a regular census of population provide information that is key to making sound decisions about national policy. A useful summary of such data is the population pyramid.