For 11–13-year-old females, the modeled requirement distribution is
These approximations for the intake and requirement distributions are very accurate when applied to values within the range of the reported percentiles. In the calculations used for the Target Median Intakes, the modeled values given above are used for intakes between the 0.5 percentile and the 99.5 percentile (tabled values for intakes are given for the 1.0 percentile and the 99 percentile) and for requirements between the 1.25 percentile and the 98.75 percentile (tabled values for requirements are given for the 2.5 percentile and the 97.5 percentile). For values outside these ranges, the cumulative distributions are set to zero for low values and one for high values.
The probability approach was used with the modeled distributions to determine the prevalence of iron inadequacy for 14–18-year-old females and 11–13-year-old females. Alternative intake distributions were assumed to be of the same distributional form but shifted to higher or lower values. Computationally, this was accomplished by adding a constant to the value of i in FI(i). The prevalence of inadequacy was computed for a range of values of the constant and the value corresponding to a 5 percent prevalence of inadequacy was determined. The value represents the shift in the intake distribution needed to achieve a 5 percent prevalence of inadequacy. The Target Median Intake is the median of the shifted distribution.
For 14–18-year-old females, the Target Median Intake is 15.92 mg/d; and 11–13-year-old females the Target Median Intake is 15.53 mg/d.