O n R e c e n s o r i n g f o r C e n s o r e d P a i r e d Data A u t h o r ( s ) : J. J a c k Lee, K e r - C h a u L i , R o b e r t M . E l a s h o f f S o u r c e : Journal of the American Statistical Association, V o l . 88, N o . 421 ( M a r . , 1993), p p . 104¬ P u b l i s h e d b y : American Statistical Association S t a b l e U R L : http://www.jstor.org/stable/2290703 Accessed: 18/05/2011 Your use of the JSTOR archive indicates your acceptance of JSTOR's Terms and Conditions of Use, available at http://www.jstor.org/page/info/about/policies/terms.jsp. JSTOR's Terms and Conditions of Use provides, in part, that unless you have obtained prior permission, you may not download an entire issue of a journal or multiple copies of articles, and you may use content in the JSTOR archive only for your personal, non-commercial use. Please contact the publisher regarding any further use of this work. Publisher contact information may be obtained at http://www.jstor.org/action/showPublisher?publisherCode=astata. Each copy of any part of a JSTOR transmission must contain the same copyright notice that appears on the screen or printed page of such transmission. JSTOR is a not-for-profit service that helps scholars, researchers, and students discover, use, and build upon a wide range of content in a trusted digital archive. We use information technology and tools to increase productivity and facilitate new forms of scholarship. For more information about JSTOR, please contact support@jstor.org. H1 American Statistical Association of the American m STOR http://www.jstor.org Statistical is collaborating with JSTOR to digitize, preserve and extend access to Journal Association.