4e5202677358e310VgnVCM100000c2b1d38dRCRDapproved/UMICH/stats/Home/People/Faculty/Faculty PublicationsCovariate Balance in Simple, Stratified and Clustered Comparative Studies1e5202677358e310VgnVCM100000c2b1d38d____Covariate Balance in Simple, Stratified and Clustered Comparative StudiesB. B. HansenJ. W. BowersbbhStatistical Science2322008219-36jjsantosjjsantos1368037552177