Quality of Evidence
"Quality of evidence" refers to the level of confidence in results across outcome studies (Cruz, Fahim, & Moore, 2015). In Public Health, a hierarchical "pyramid of evidence" is often used to assess quality of evidence. A pyramid of evidence ranks the validity of evidence based on the study design with weakest studies (most susceptible to threats) at the bottom and strongest studies (least susceptible to threats) at the top.
You might also consider using critical appraisal tools to evaluate evidence. Critical appraisal is the careful examination of research methods. The appraisal process usually involves judging methods by a list of questions or criteria. Critical appraisal tools and resources can be found at the links provided below.
Cruz, J. E., Fahim, G., & Moore, K. (2015). Practice guideline development, grading, and assessment. Pharmacy and Therapeutics, 40(12), 854-857. Retrieved from http://www.ncbi.nlm.nih.gov/pmc/articles/PMC4671471/