Stetler and colleagues (1998) describe six different levels of research. Level I refers to a meta-analysis of multiple
controlled studies and is the strongest type of research. Level II illustrates an individual experimental study. Level III
indicates a quasi-experimental study, such as nonrandomized controlled single group pre-post test, time series, or matched
case-controlled studies. Level IV describes non-experimental study, such as correlational descriptive and qualitative or
case studies. Level V indicates a case report or program evaluation data. Lastly, Level VI describes reviewed evidence,
based on the opinions of respected authorities. Additionally, “quality from any level can range from A to D and reflects
basic scientific credibility of the overall study/project. An A reflects a very well designed study/project. If quality is rated
as a D, it is automatically eliminated from consideration” [14]. Data extracted from the included studies is presented in
Table 1 and consists of: (a) sample characteristics, (b) description of the intervention, (c) outcome measures, (d) measurement
points, (e) theoretical framework, (f) results of the study, and (g) level of evidence. The data was extracted from the
studies by the authors of this review.