“…Downs and Black (1998) stated that health care research must use a nonrandomized method and a checklist for non-RCT studies because current checklists lack detailed subscales and ignore the external validity of trials. Their checklist is now used for systematic reviews in rehabilitation (McCabe et al, 2007;Robbins, Houghton, Woodbury, & Brown, 2006;Teasell et al, 2007) and other fields (Hartling, Brison, Crumley, Klassen, & Pickett, 2004;Malcomson, Dunwoody, & Lowe-Strong, 2007). The Downs and Black checklist consists of 27 questions with four subscales: Reporting, External Validity, Bias, and Confounding.…”