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  2. Incidence (epidemiology) - Wikipedia

    en.wikipedia.org/wiki/Incidence_(epidemiology)

    Incidence (epidemiology) In epidemiology, incidence is a measure of the probability of occurrence of a given medical condition in a population within a specified period of time. Although sometimes loosely expressed simply as the number of new cases during some time period, it is better expressed as a proportion or a rate [1] with a denominator .

  3. Metropolitan statistical area - Wikipedia

    en.wikipedia.org/wiki/Metropolitan_Statistical_Area

    In the United States, a metropolitan statistical area (MSA) is a geographical region with a relatively high population density at its core and close economic ties throughout the region. [1] [2] Such regions are not legally incorporated as a city or town would be and are not legal administrative divisions like counties or separate entities such ...

  4. Expected value - Wikipedia

    en.wikipedia.org/wiki/Expected_value

    v. t. e. In probability theory, the expected value (also called expectation, expectancy, expectation operator, mathematical expectation, mean, expectation value, or first moment) is a generalization of the weighted average. Informally, the expected value is the arithmetic mean of the possible values a random variable can take, weighted by the ...

  5. Population inversion - Wikipedia

    en.wikipedia.org/wiki/Population_inversion

    Population inversion. In physics, specifically statistical mechanics, a population inversion occurs while a system (such as a group of atoms or molecules) exists in a state in which more members of the system are in higher, excited states than in lower, unexcited energy states. It is called an "inversion" because in many familiar and commonly ...

  6. Gaza Strip - Wikipedia

    en.wikipedia.org/wiki/Gaza_Strip

    The Gaza Strip is 41 kilometres (25 miles) long, from 6 to 12 km (3.7 to 7.5 mi) wide, and has a total area of 365 km 2 (141 sq mi). [26] [27] With around 2 million Palestinians [28] on approximately 365 km 2 (141 sq mi) of land, Gaza has one of the world's highest population densities.

  7. Center of population - Wikipedia

    en.wikipedia.org/wiki/Center_of_population

    Center of population. In demographics, the center of population (or population center) of a region is a geographical point that describes a centerpoint of the region's population. There are several ways of defining such a "center point", leading to different geographical locations; these are often confused. [1]

  8. 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 ...

  9. Median - Wikipedia

    en.wikipedia.org/wiki/Median

    Median. Finding the median in sets of data with an odd and even number of values. In statistics and probability theory, the median is the value separating the higher half from the lower half of a data sample, a population, or a probability distribution. For a data set, it may be thought of as "the middle" value.