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aDepartment of Statistics, Columbia University, New York, NY; bDepartment of Health Care Policy, Harvard Medical School, Boston, MA; and cDepartment of Statistics, Faculty of Arts and Sciences, Harvard University, Cambridge, MA.
Editor’s Note: Related article appears on p. 802.
The authors report no conflicts of interest.
Supported by a grant from the Alfred P. Sloan Foundation.
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Correspondence: José R. Zubizarreta, Department of Health Care Policy, Harvard Medical School, 180 Longwood Avenue, 307-D Boston, MA. E-mail: email@example.com.