This report describes the statistical methodologies for the 2018 Department of Defense Civilian Employee Workplace and Gender Relations Survey (2018 WGRC). The first section describes the sample design and selection of the sample. The second section describes weighting and variance estimation. The third section describes the statistical tests used for the 2018 WGRC. The fourth section describes the calculation of cooperation, completion, and response rates for the full sample and population subgroups. The fifth section summarizes the findings from the non-response bias analysis. Estimates for select survey questions are found in the Department of Defense Civilian Employee Workplace and Gender Relations Report for Fiscal Year 2018: Biennial Report to Congress (DoD, 2020) posted publicly at http://diversity.defense.gov/Documents.