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The ratio of the number of events in the population being studied during a certain time period to the estimated population size midway through that time period.



Guide for use:

R =d/n

R  is the crude rate for the population being studied,
d is the number of events for that population group,
n is the total population for that population group.

Population health and health services research:
Required to calculate population rates, such as incidence rates, prevalence rates, mortality rates and health service utilisation rates.


Australian Institute of Health and Welfare


Crude rates are generally multiplied by 1,000 or 100,000 to avoid small decimal fractions. It is then called the crude rate per 1,000 or 100,000 population.


Textbooks of epidemiology, demography and biostatistics.

The presentation of formulae in this data element is based on the notation used in Armitage P & Berry G 1994. Statistical Methods in Medical Research. Oxford: Blackwell Scientific Publications.

See also Age-standardised rate

This content Based on Australian Institute of Health and Welfare material. Attribution provided as required under the AIHW CC-BY licence.

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