Evidence-Based Practice (EBP) is the integration of clinical experience and patient preferences with the best available research information.
When doing EBM, it is preferable to obtain evidence from as high up the 'hierarchy of evidence' as possible.
* Image used with the kind permission of Dr. Sam Keim.
(Below this level 5 would be evidence from research such as animal studies and 'bench science')
The 'gold standard' for EBM is the randomized controlled trial (RCT), and further, systematic reviews (often involving meta-analysis) carried out on groups of RCTs.
Statistically-speaking, those types of studies offer better 'evidence', because when done correctly, they offer the best chance to avoid the various types of bias amd confounders that occur when carrying out research. - the type of evidence generated by RCTs and SRs make it easier to determine whether that research's data has sufficiently disproven the researchers' 'null-hypothesis'.