The term “evidence” generally refers to “unobserved as well as observed phenomena if the former reflects signs or indications that support, substantiate, or prove their existence, accuracy, or truth” (Cournoyer, 2004, p. 3). However, phenomena that are unexamined or unobserved are considered less credible than evidence derived from observation, experience, or experimentation (Cournoyer, 2004). Those phenomena subject to observation include clinical experience, results from own practice evaluation, expert opinion, case studies, randomized clinical trials, and meta-analyses (Cournoyer, 2004; Pollio, 2002).