Box 4-2 The EAR cut-point method—when it works
The EAR cut-point method works best (produces an almost unbiased estimate of prevalence of nutrient inadequacy) when:
intakes and requirements are independent
the requirement distribution is symmetrical around the EAR
the variance in intakes is larger than the variance of requirements
true prevalence of inadequacy in the population is no smaller than 8 to 10 percent or no larger than 90 to 92 percent.
If the true prevalence in the group is about 50 percent—so that the mean intake is approximately equal to the EAR—then the EAR cut-point method results in almost unbiased estimates of prevalence of inadequacy even if conditions 1 and 3 are not met (see Appendix D).1
The EAR cut-point method—when it does not work
What happens when the assumptions required for the cut-point method are not met? In the following section, examples are provided of situations in which the assumptions do not hold. The cut-point method can either underestimate or overestimate the population prevalence of inadequacy under such circumstances.