TABLE B-1 Values for the Ratio D/SDD and Corresponding Probability of Correctly Concluding that Usual Intake Is Adequate or Inadequate
Criterion |
Conclusion |
Probability of Correct Conclusion |
D/SD_{D}> 2.00 |
Usual intake is adequate |
0.98 |
D/SD_{D}> 1.65 |
Usual intake is adequate |
0.95 |
D/SD_{D}> 1.50 |
Usual intake is adequate |
0.93 |
D/SD_{D}> 1.00 |
Usual intake is adequate |
0.85 |
D/SD_{D}> 0.50 |
Usual intake is adequate |
0.70 |
D/SD_{D}> 0.00 |
Usual intake is adequate (inadequate) |
0.50 |
D/SD_{D}< −0.50 |
Usual intake is inadequate |
0.70 |
D/SD_{D}< −1.00 |
Usual intake is inadequate |
0.85 |
D/SD_{D}< −1.50 |
Usual intake is inadequate |
0.93 |
D/SD_{D}< −1.65 |
Usual intake is inadequate |
0.95 |
D/SD_{D}< −2.00 |
Usual intake is inadequate |
0.98 |
SOURCE: Adapted from Snedecor and Cochran (1980). |
and is only approximate. The assumptions that are implicit in the criterion include:
The distribution of daily intakes Y around the mean intake is approximately normal, or at least symmetrical, for the individual. Any nutrient with a skewed distribution of daily intakes would not satisfy this assumption, such as those nutrients in Table B-2, Table B-3, Table B-4 through Table B-5 with a CV larger than about 60 to 70 percent.
The distribution of requirements in the group is approximately normal.
The daily intake Y accurately reflects the individual's true intake of the nutrient for the day.
A reliable estimate of the day-to-day variability in intake for the individual is available.
Intakes are independent of requirements.
In probabilistic terms, the value of 1 for the ratio D/SD_{D} corresponds to an approximate 0.15 p-value for the test of the hypothesis that y > ρ. That is, when it is concluded that intake is adequate, there is approximately an 85 percent chance of reaching the correct conclusion and approximately a 15 percent chance of making a mistake (erroneously concluding that intake is adequate). Because the criterion is formulated on this probabilistic basis, the level of