“…For example, a common weakness of the studies included was failure to blind those grading the academic performance when ratings were subjective. Of the studies that used either subjective methods 14,15,17,25,26,29,32,34 or failed to describe assessment methods, 16,20,21,23,24,27,30,31 only 1 group of investigators blinded the graders. 15 Another potential weakness of the studies under review is nonrandom exclusion of participants.…”