title: Experiments versus quasi-experiments: do they yield the same answer?
authors.affiliation: Department of Psychology Memphis State University, TN 38152, USA.
authors.forename: W R
authors.initials: WR
authors.lastname: Shadish
authors.forename: D T
authors.initials: DT
authors.lastname: Heinsman
mesh_terms: D006801:Humans; D008962:Models, Theoretical; D011897:Random Allocation; D016032:Randomized Controlled Trials as Topic / Q000706:statistics & numerical data; D012107:Research Design; D019966:Substance-Related Disorders / Q000517:prevention & control