<P> A 2007 analysis of 1,016 systematic reviews from all 50 Cochrane Collaboration Review Groups found that 44% of the reviews concluded that the intervention was likely to be beneficial, 7% concluded that the intervention was likely to be harmful, and 49% concluded that evidence did not support either benefit or harm . 96% recommended further research . A 2001 review of 160 Cochrane systematic reviews (excluding complementary treatments) in the 1998 database revealed that, according to two readers, 41% concluded positive or possibly positive effect, 20% concluded evidence of no effect, 8% concluded net harmful effects, and 21% of the reviews concluded insufficient evidence . A review of 145 alternative medicine Cochrane reviews using the 2004 database revealed that 38.4% concluded positive effect or possibly positive (12.4%) effect, 4.8% concluded no effect, 0.7% concluded harmful effect, and 56.6% concluded insufficient evidence . In 2017, a study assessed the role of systimatic reviews produced by Cochrane Collaboration to inform US private payers' policies making; it showed that though medical policy documents of major US private were informed by Cochrane systematic review; there was still scope to encourage the further usage . </P> <P> Evidence quality can be assessed based on the source type (from meta - analyses and systematic reviews of triple - blind randomized clinical trials with concealment of allocation and no attrition at the top end, down to conventional wisdom at the bottom), as well as other factors including statistical validity, clinical relevance, currency, and peer - review acceptance . Evidence - based medicine categorizes different types of clinical evidence and rates or grades them according to the strength of their freedom from the various biases that beset medical research . For example, the strongest evidence for therapeutic interventions is provided by systematic review of randomized, triple - blind, placebo - controlled trials with allocation concealment and complete follow - up involving a homogeneous patient population and medical condition . In contrast, patient testimonials, case reports, and even expert opinion (however some critics have argued that expert opinion "does not belong in the rankings of the quality of empirical evidence because it does not represent a form of empirical evidence" and continue that "expert opinion would seem to be a separate, complex type of knowledge that would not fit into hierarchies otherwise limited to empirical evidence alone .") have little value as proof because of the placebo effect, the biases inherent in observation and reporting of cases, difficulties in ascertaining who is an expert and more . </P> <P> Several organizations have developed grading systems for assessing the quality of evidence . For example, in 1989 the U.S. Preventive Services Task Force (USPSTF) put forth the following: </P> <Ul> <Li> Level I: Evidence obtained from at least one properly designed randomized controlled trial . </Li> <Li> Level II - 1: Evidence obtained from well - designed controlled trials without randomization . </Li> <Li> Level II - 2: Evidence obtained from well - designed cohort studies or case - control studies, preferably from more than one center or research group . </Li> <Li> Level II - 3: Evidence obtained from multiple time series designs with or without the intervention . Dramatic results in uncontrolled trials might also be regarded as this type of evidence . </Li> <Li> Level III: Opinions of respected authorities, based on clinical experience, descriptive studies, or reports of expert committees . </Li> </Ul>

Who made a recommendation for a hospital based on his findings