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Ralph E. Folsom

Chief Scientist, Statistical, Survey, and Computing Sciences

Ralph Folsom, PhD, is an expert in the design and analysis of complex probability samples. Working on the nation’s largest household survey (the National Survey on Drug Use and Health or NSDUH), Dr. Folsom initiated innovative weight adjustment methods based on his logistic response propensity and exponential poststratification models. This pioneering work led to the sophisticated GEM weight adjustment methods currently employed for NSDUH. Dr. Folsom also introduced model-based imputations for missing frequency of use and income data items, and he has been an influential collaborator in the development of NSDUH’s current Predictive Mean Neighborhoods (PMN) imputation methodology. Dr. Folsom has recently led RTI’s innovative work in small area estimation research. In addition to his innovative work on many complex survey efforts, Dr. Folsom has made significant contributions to the development of RTI’s computer software for survey data analysis, SUDAAN.


PhD, Biostatistics, University of North Carolina; MS, Statistics, Iowa State University; BS, Wildlife Management, Texas A&M University.

Latest Publications

Cooley, P.C., Clark, R.F., & Folsom, R.E. (May 2014). Assessing gene-environment interactions in genome-wide association studies: Statistical approaches: RTI Press Publication No. RR-0022-1405. Research Triangle Park, NC: RTI Press.
Vaish, A.K., Folsom, R., Sathe, N.S., Spagnola, K.E., & Hughes, A. (2013). An Empirical Study to Evaluate the Performance of Synthetic Estimates of Substance Use in the National Survey of Drug Use and Health. Presented at JSM 2013, Montréal, Québec, Aug 2013.
Cooley, P., Gaddis, N., Folsom, R., & Wagener, D. (2012). Conducting genome-wide association studies: Epistasis scenarios. Journal of Proteomics & Bioinformatics, 5 (10):245-251.
Cooley, P., Clark, R., Folsom, R., & Page, G. (2010). Genetic inheritance and Genome Wide Association statistical test performance. Journal of Proteomics & Bioinformatics, 3 (12):321-325.
View all publications by Ralph E. Folsom (27)


  • Complex Sample Design and Analysis
  • Survey Weight Adjustment
  • Small Area Estimation
  • Missing Data Imputation