This study employed hierarchical linear models (HLM) to investigate Peer-Led Guided Inquiry (PLGI), a teaching practice combining cooperative learning and inquiry and tailored for a large class. Ultimately, the study provided an example of the effective introduction of a reform pedagogical approach in a large class setting. In the narrative, the strengths of HLM as a statistical technique are discussed in the context of pedagogical reforms, and the case is made for the use of HLM in rigorous determinations of both effectiveness and equity associated with reform practices. The implementation of PLGI in a college-level general chemistry course is also described. For the study, two general HLM models suited to investigating reform were developed and utilized to examine the effectiveness and equity of PLGI as implemented in this setting. The models showed that the reform was associated with statistically significant improvement over traditional pedagogy in terms of academic performance on multiple measures, but achieving equity remained elusive: the consequences of pre-existing achievement gaps did not lessen as a result of reform implementation. The analysis led to several implications for educational research, particularly in terms of evaluating pedagogical reforms, as well as for teaching. Choosing effective and equitable pedagogies for classroom implementation remains a critical goal for classes of any size. (Contains 9 tables.)