The adjusted estimate of the usual intake distribution has a smaller variance than does the estimate obtained using one day of intake data. This is to be expected because one of the features of the method (and also of the method proposed by NRC) is that it partially removes the day-to-day variability in intakes. Thus, the estimated usual intake distribution obtained by applying the adjustment has a variance that reflects only the between-person variability in intakes, whereas the estimate obtained using one-day data has a variance that is inflated by day-to-day variability.
The shapes of the two distributions in Figure 4-12 are quite different. More importantly, the conclusions drawn about the proportion of individuals in the group whose intakes of vitamin B6 are inadequate also differ, depending on which estimate of the usual intake
FIGURE 4-12 Estimates of a usual intake distribution of vitamin B6 obtained from one day of intake data and adjusted using replicate intake data via the Iowa State University method. The y-axis shows the likelihood of each level of intake in the population.