ABSTRACT
This chapter explains, first, what it means to talk about categorical versus "on average" differences. With this background, we will be prepared to explore what Statement B means, and why it is misleading in the absence of more information about how much different, and how much similar are the genders. In a highly gender-differentiated society, one may be able to categorize an adult individual by sex, with an extremely high degree of reliability, merely by observing variables such as hair length, type of apparel, or type of work—or conversely, accurately predict an individual's hair length, clothing, or type of work based on the individual's sex. The chapter focuses on first is the size of the gap between the proportions or means. The second is how the distributions compare in terms of similarities. A degree of statistical sophistication is required for understanding "gender difference at the aggregate level" (GDA).
