“…Thus, heterogeneity bias occurs when researchers do not account for variations across groups. However, only until recently, researchers have begun to analyze differential effects of student aid packages by groups of students and type of financial aid package (Avery & Hoxby, 2004;Callender & Jackson, 2005;Kim, 2004;Mendez & Mendoza, 2008;Mendez, Mendoza, & Malcolm, 2011;Mendoza, Mendez, & Malcolm, 2009;Paulsen & St. John, 2002;Price, 2004). Moreover, Chen (2008) goes a step further, suggesting that research often takes limited consideration of the longitudinal characteristics of student departure and the possible time-varying effects of aid.…”