• Systematic review to determine whether participation in a trial influences outcome. 

      Vist, Gunn Elisabeth; Hagen, Kåre Birger; Devereaux, P J; Bryant, Dianne; Kristoffersen, Doris Tove; Oxman, Andrew David (Journal article, 2005-05-21)
      OBJECTIVE: To systematically compare the outcomes of participants in randomised controlled trials (RCTs) with those in comparable non-participants who received the same or similar treatment. DATA SOURCES: Bibliographic ...