women requires use of the probability approach because of the highly skewed nature of the requirement distribution. Because of the very high correlation between intakes and requirements, energy is the one nutrient for which neither the probability approach nor the cut-point method can be used to assess adequacy. The prevalence of nutrient inadequacy for a group will usually be overestimated by either method if dietary intake data are not adjusted for day-to-day within-person variation. Thus, a minimum of two nonconsecutive or three consecutive days of intake data on at least a representative sample of the group is needed for dietary assessment of groups.