The Penn State Methodology Center was continuously funded through National Institute on Drug Abuse Center of Excellence awards from 1996-2021. These grants, P50 DA039838 and P50 DA010075, served as the cornerstone of Methodology Center funding and enabled The Methodology Center to become an internationally recognized leader in the development and dissemination of methods for experimental design and data analysis in the social, health, and behavioral sciences. Together, Drs. Bethany Bray, John Dziak, and Stephanie Lanza led the development and application of innovative latent class modeling approaches for many years as investigators in The Methodology Center. Much of the information and many of the resources provided in this Knowledge Base were developed in The Methodology Center.