Figure 3. Predicted probability of apnea by weeks postconceptual age for all three models: model 1 (solid line) all infants; model 2 (irregular line) all nonanemic infants; and model 3 (broken line) patients who were not anemic and did not experience apnea in recovery room. The risk for apnea decreases markedly when patients with anemia (model 2) are eliminated, and the risk diminishes further if patients with apnea in recovery room (model 3) also are eliminated. See text for discussion.