The "Stabilizing Subgroup Proficiency Results to Improve the Identification of Low-Performing Schools" study used Bayesian stabilization to improve the reliability (long-term stability) of subgroup proficiency measures that the Pennsylvania Department of Education (PDE) uses to identify schools for Targeted Support and Improvement (TSI) or Additional Targeted Support and Improvement (ATSI). The Every Student Succeeds Act requires states to designate schools with low-performing student subgroups for TSI or ATSI. This document presents the following appendixes that accompany the study: (1) Literature review; (2) Data and methods; and (3) Supplemental Results. [For the full report, see ED626539. For the Study Snapshot, see ED626540.]