This chapter offers a concise, systematic introduction to quantification in sex differences research. The chapter reviews the main methods used to measure sex differences and similarities, including standardized distances (Cohen’s d and Mahalanobis’ D), indices of overlap, variance ratios, and tail ratios. Some less common approaches (e.g., relative distribution methods, taxometrics) are also reviewed and discussed. The chapter examines the strengths and limitations of each method, considers various statistical and methodological factors that may either inflate or deflate the size of sex differences, and discusses the available options to minimize their influence. Other topics addressed include the effective visualization of sex differences/similarities, and the rationale for treating sex as a binary variable despite the complexities of sex-related identity and behavior.
