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THE EAR CUT-POINT METHOD

The Estimated Average Requirement (EAR) cut-point method, proposed by Beaton (1994), is a shortcut derived from the probability approach described above. In contrast to the probability approach, the EAR cut-point method simply requires the distribution of requirements to be symmetrical. It is not necessary to know the actual variance of the requirement distribution, only its size relative to the intake variance. Like the probability approach, the EAR cut-point method requires knowledge of the median requirement (the EAR) for the nutrient and the distribution of usual intakes in the population.

Table 4-1 summarizes whether nutrients for which Dietary Reference Intakes (DRIs) have been established as of this writing (IOM, 1997, 1998b, 2000) meet the assumptions necessary to apply the EAR cut-point method for assessing the prevalence of inadequacy for groups.

The cut-point method is very simple. The population prevalence of inadequate intakes is computed as the proportion of the group

Box 4-1 The EAR cut-point method—what it is, and why it works

This method is very straightforward, and surprisingly, can sometimes be as accurate as the probability approach. With this method, the population prevalence of inadequate intakes is simply the proportion of the population with intakes below the median requirement (EAR). Modest departures from any of the assumptions listed below are likely to have only a small effect on the performance of the EAR cut-point method. However, the method does not work with nutrients such as energy where it is known that intakes and requirements are highly correlated, or with iron requirements in menstruating women where the requirement distribution is known to be highly skewed rather than symmetrical.

This method works well when:

  • intakes are accurately measured

  • actual prevalence in the group is neither very low nor very high

  • estimated usual intakes of individuals are independent of each individual 's requirement

  • the distribution of requirements is approximately symmetrical

  • variability in intakes among individuals in the group is greater than the variability in requirements of the individuals.



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