RT Journal Article SR Electronic T1 Adding cost to number needed to treat: the COPE statistic JF Evidence Based Medicine JO Evid Based Med FD BMJ Publishing Group Ltd SP 101 OP 102 DO 10.1136/ebm.12.4.101 VO 12 IS 4 A1 Rohan Maharaj YR 2007 UL http://ebm.bmj.com/content/12/4/101.abstract AB