A population is a collection of units being studied. This might be the set of all people in a country. Units can be people, places, objects, years, drugs, or many other things. The term population is also used for the infinite population of all possible results of a sequence of statistical trials, for example, tossing a coin. Much of statistics is concerned with estimating numerical properties (parameters) of an entire population from a random sample of units from the population.

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