Group-level means as a function of group gender composition. Three indices of within-group “connectedness” are represented along the left: group density (top-left), within-group reciprocity (middle-left), and within-group transitivity (bottom-left). In the middle panels are peer group means on examples of a demographic (free/reduced-price lunch, top-middle), family (family relations, middle-middle), and behavioral variable (school grades, bottom-middle). Finally, along the right are peer group means on three problem behaviors: cigarette use (top-right), alcohol use (middle-right), and delinquency (bottom-right).