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clude that the intervention was associated with a statistically significant decrease in the prevalence of inadequacy. If the standard deviations are large (e.g., 10 percent), then one could not conclude that the 7 percent decrease was significant or that the intervention worked.

Finally, the part of the intake distribution being assessed affects the error associated with the estimate. Values in the tail of the distribution are harder to estimate (i.e., estimates are less precise) than values in the center of a distribution (such as means or medians). Thus, estimating prevalence of inadequacy of a nutrient is expected to be less precise for nutrients for which prevalence of inadequacy in the group is very low or very high (e.g., 5 or 95 percent) compared with nutrients for which prevalence of inadequacy is towards the center of the distribution (e.g., 30 to 70 percent) for the same sampling design and same estimation method.

SUMMARY

Users of the Dietary Reference Intakes (DRIs) have many opportunities to minimize errors when assessing group and individual intakes. This chapter has focused on ways to increase the accuracy of both the requirement estimates (by considering the specific characteristics of the individual or the population) and the intake estimates (by ensuring that dietary data are complete, portions are correctly specified, and food composition data are accurate) and the importance of an appropriate sampling plan for group intakes.

Although users of the DRIs should strive to minimize errors, perfection usually is not possible or necessary. Comparing high-quality intake data with tailored requirement data to assess intakes is a meaningful undertaking and can, at a minimum, identify nutrients likely to be either under- or overconsumed by the individual or the group of interest.



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