To accurately assess the effectiveness of an intervention, participants in the treatment and control groups should be treated equally in all respects except for the intervention being tested. In this study, there were some differences between the conventional group and the color-coded group in addition to the color-coding intervention. First, participants in the color-coded group were presented with both the children's formulation of acetaminophen and the infant's formulation, but only the children's formulation was color coded, and only the color-coded syringe corresponding to the children's formulation was offered. Although this was not explicitly stated, we assume that, because only the color-coded syringe was offered, the parents of young infants in this group were directed to use the children's formulation. In contrast, in the conventional group, both the infant's and children's formulations of acetaminophen were offered, and the decision to use either formulation was based solely on the parent's choice. Since the dosing of the children's and infant's formulations differs substantially, the comparisons between the groups may be biased.