intake days (n) available for the individual was very large. In practice an individual 's usual intake is seldom known; instead, the individual's observed mean intake is used as an estimate of the individual's usual intake y.
When assessing an individual's dietary intake, usual intake and not observed intake should be compared with the requirement to determine whether the intake is adequate (or whether it exceeds the UL).
Assessing the adequacy of an individual's intake of a nutrient by using only dietary information is difficult because neither the usual intake nor the actual requirement of the individual is known. The approach detailed here for assessing the adequacy of an individual's intake requires four types of information: the median requirement of the nutrient for the individual's life stage and gender group (the EAR), the variability in the requirement for the individual's life stage and gender group, the mean observed intake for the individual, and the day-to-day variability in intake of the nutrient for the individual. By combining this information appropriately, a method for estimating the adequacy of an individual 's usual intake of a nutrient can be derived. A similar approach may be used to compare observed intake to an AI or UL, and will be discussed later in this appendix.
Following are the assumptions for the statistical approach to evaluating the adequacy of an individual's observed intake:
The Estimated Average Requirement (EAR) is the best estimate of the individual's unobservable true requirement, denoted by ρ. The estimate for the individual's requirement is denoted by r, and r is set to be equal to the EAR of the appropriate life stage and gender group. The standard deviation of requirements in the population, denoted by SDr, is proportional to the uncertainty about how precisely r estimates ρ. If every individual had the exact same requirement for the nutrient, then r (which is set to be equal to the EAR) would be a precise estimate of each individual's requirement. Because individuals vary in their requirement for a nutrient, it is important to consider the extent of the variability in the group; the SDr is an indicator of how variable requirements are in the group.