Observed and modeled risk for ferritin levels of less than 12 ng/mL in African American, Asian, and Hispanic subjects. Plots show the observed prevalence of ferritin levels of less than 12 ng/mL (A, C, E) for African American, Asian, and Hispanic subjects, stratified by sex. Residuals from logistic regression models that omit age and sex show the unexplained variability for ferritin levels of less than 12 ng/mL (B, D, F) for each pairing of sex and age. [Color figure can be viewed at wileyonlinelibrary.com]