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National Information Center on Health Services Research and Health Care Technology (NICHSR)

Understanding the “Reference Population of a statistical result”
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We can think of the reference population as described by a number of factors. For example, a reference population could be defined by:
  • A chunk of ground or geographic area where an activity occurred—for example, do we need national statistics or a breakdown by state, county or city.
  • A time period—for example, do we need current information or a trend over time—if so what is the time period that needs to be included?
  • The social standing and affiliations of the people covered—for example, do we need statistics for the entire population, those who live in households, those of particular age groups, with a risk factor or suffering from a particular disorder?

This diagram illustrates the reference population for elderly HIV AIDS persons living in New York City. A statistical procedure that aims to estimate the characteristics of this population requires different approaches than one that covers the entire HIV positive population, the population of the US or all age groups. Choices made regarding the reference population will shape the kinds of statistics that are available.
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