[0] Moderate [1] Studies of strong design with minor methodological concerns OR only studies of weaker study design for question [2] Inconsistency among results of studies with strong design, OR consistency with minor exceptions across studies of weaker design [3] Several studies by independent investigators Doubts about adequacy of sample size to avoid Type I and Type II error [5] Minor doubts about generalizability [4] 
Some doubt about the statistical or clinical significance of the effect