ABSTRACT
This chapter describes one of the three components of evidence-based practice (EBP): scientific evidence. Scientific evidence is available in various forms. Historically, the most established source of scientific evidence has been primary research, traditionally a responsibility of universities and academic institutions. The chapter introduces the concept of the hierarchy of evidence. It discusses two main sections: primary research, including systematic reviews and meta-analyses; and tailored or packaged evidence. Systematic research reviews and meta-analysis reports, as well their plain-language summaries, are disseminated by Cochrane and Campbell collaborations and other institutions. Research designs are tools employed by scientists to observe and organize the human experience and societal phenomena. The chapter concludes with a few words of warning: It is good science to recognize the limits of any gold standard, because a major problem in science is that it is impossible to know with 100" certainty what the truth is in any given research question.
