title: Statistical and design issues in studies of groups.
authors.affiliation: Harborview Injury Prevention and Research Center and the Department of Epidemiology, University of Washington, Seattle 98104-2499, USA. peterc@u.washington.edu
authors.forename: P
authors.initials: P
authors.lastname: Cummings
authors.forename: T D
authors.initials: TD
authors.lastname: Koepsell
mesh_terms: D005069:Evaluation Studies as Topic; D006801:Humans; D012107:Research Design; D013223:Statistics as Topic; D014947:Wounds and Injuries / Q000517:prevention & control*