When you have (or imagine you have) access to the entire population of interest, perhaps every person in a country or every user of a device, and can calculate the standard deviation (s.d., σ) of some facet of them all; that is √ ( &;Sigma (xi–μ)2))/N – where xi are the individual measurements of the facets, μ is the arithmetic mean (μ) and N the number of people in the entire population.
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