nutrient is normally distributed, the EAR plus 2 SDs of the EAR equals the RDA:
RDA = EAR + 2 SDEAR.
If data about variability in requirements are insufficient to calculate an SD, a coefficient of variation (CVEAR) of 10 percent will be ordinarily assumed. Because
CVEAR = SDEAR/EAR,
SD = (EAR × CVEAR),
the resulting equation for the RDA is
RDA = EAR + 2 (0.1 × EAR)
RDA = 1.2 × EAR.
The assumption of a 10 percent CV is based on extensive data on the variation in basal metabolic rate (FAO/WHO/UNA, 1985; Garby and Lammert, 1984), which contributes about two-thirds of the daily energy expenditure of many individuals residing in Canada and the United States (Elia, 1992) and on the similar CV of 12.5 percent estimated for the protein requirements in adults (FAO/ WHO/UNA, 1985). If there is evidence of greater variation, a larger CV will be assumed. If the distribution of the nutrient requirement is known to be skewed for a population, other approaches may be used to find the ninety-seventh percentile to set the RDA. In all cases the method used to derive the RDA from the EAR is stated.
For the B vitamins there are few direct data on the requirements of children. Thus, EARs and RDAs for children are based on extrapolations from adult values. The method is described in Chapter 2.
Together with an estimate of the variance of intake, the EAR may also be used in the assessment of the intake of groups or in planning for the intake of groups (Beaton, 1994) (see Chapter 13).