individual's usual intake.
There is day-to-day variation in intake for an individual. The within-person standard deviation of intakes is an indicator of how much observed intake may deviate from usual intake.
Inferences about the adequacy of an individual's diet can be made by looking at the difference between observed intake and the median requirement. If this difference is large and positive, that is, if observed intake is much greater than the median requirement, then it is likely that an individual's intake is adequate. Conversely, if the difference is large and negative, that is, observed intake is much less than the median requirement, then it is likely that an individual's intake is not adequate. In between there is considerable uncertainty about the adequacy of the individual's intake.
For practical purposes, many users of the DRIs may find it useful to consider that observed intakes below the EAR very likely need to be improved (because the probability of adequacy is 50 percent or less), and those between the EAR and the Recommended Dietary Allowance (RDA) probably need to be improved (because the probability of adequacy is less than 97 to 98 percent). Only if intakes have been observed for a large number of days and are at or above the RDA, or observed intakes for fewer days are well above the RDA, should one have a high level of confidence that the intake is adequate. It is hoped that computer software will be developed that will determine these probabilities (as described in Appendix B), thus offering more objective alternatives when individual intakes are evaluated.
Some nutrients have an Adequate Intake (AI) because the evidence was not sufficient to establish an EAR and thus an RDA for the nutrient in question. The approach described above for the EAR cannot be used for nutrients that have an AI. However, a statistically based hypothesis testing procedure for comparing observed intake to the AI may be used. This is a simple z-test, which is constructed using the standard deviation of daily intake of the nutrient.
What conclusions can be drawn about the adequacy of individual intakes for nutrients with AIs? First, if an individual's usual intake equals or exceeds the AI, it can be concluded that the diet is almost certainly adequate. If, however, their intake falls below the AI, no quantitative (or qualitative) estimate can be made of the probability of nutrient inadequacy. Professional judgment, based on additional