RT Journal Article SR Electronic T1 Clarifying the interrupted time series study design JF BMJ Quality & Safety JO BMJ Qual Saf FD BMJ Publishing Group Ltd SP 475 OP 475 DO 10.1136/bmjqs-2015-004122 VO 24 IS 7 A1 Svoronos, Theodore A1 Fretheim, Atle YR 2015 UL http://qualitysafety.bmj.com/content/24/7/475.1.abstract AB