Individuals exert influence on – and are influenced by – those within their social environment. When research focuses on dyads, as is often the case in developmental research (e.g., parent-child, sibling-sibling), educational research (e.g., teacher-student), and relationship research (e.g., romantic partners, roommates), it is likely that the responses of individuals within each dyad are not independent. This is because individuals are likely influenced by the characteristics of their dyad and the qualities of the other dyad member (Little and Card 2005). When this lack of independence (referred to as interdependence) is unaccounted for, it can bias significance tests (e.g., increase type I errors; Kenny and Judd 1986). The APIM...