The "Understanding Access to and Participation in Dual Enrollment by Locale and Income Level" study explored patterns in dual enrollment access and participation for the 2017/18 school year in the REL Central states (Colorado, Kansas, Missouri, Nebraska, North Dakota, South Dakota, and Wyoming). The report also revealed how dual enrollment access and participation varied with school characteristics, including school locale (city, suburban, town, or rural) and percentage of students from low-income households. The study found that dual enrollment access and participation were higher in the REL Central region than nationally. Additionally, students in rural and city locales tended to have lower dual enrollment access than did their peers in town and suburban locales. This document presents the following appendix that accompanies the study: (1) Data and methodology. [For the full report, see ED612869. For the Study Brief, see ED612870. For the Study Snapshot, see ED612871.]