Table 3Definitions of overall quality ratings

Quality RatingDescription
GoodA study with the least bias; results are considered valid. A good study has a clear description of the population, setting, interventions, and comparison groups; uses a valid approach to allocate patients to alternative treatments; has a low dropout rate; and uses appropriate means to prevent bias, measure outcomes, and analyze and report results.
FairA study that is susceptible to some bias but probably not enough to invalidate the results. The study may be missing information, making it difficult to assess limitations and potential problems. As the fair-quality category is broad, studies with this rating vary in their strengths and weaknesses. The results of some fair-quality studies are possibly valid, while others are probably valid.
PoorA study with significant bias that may invalidate the results. These studies have serious errors in design, analysis, or reporting; have large amounts of missing information; or have discrepancies in reporting. The results of a poor-quality study are at least as likely to reflect flaws in the study design as to indicate true differences between the compared interventions.

From: Methods

Cover of Pulmonary Arterial Hypertension: Screening, Management, and Treatment
Pulmonary Arterial Hypertension: Screening, Management, and Treatment [Internet].
Comparative Effectiveness Reviews, No. 117.
McCrory DC, Coeytaux RR, Schmit KM, et al.

NCBI Bookshelf. A service of the National Library of Medicine, National Institutes of Health.