Levels of Evidence
|Level||Type of Evidence|
|Ia||Evidence obtained from meta-analysis or systematic review of randomized controlled trials.|
|Ib||Evidence obtained from at least one randomized controlled trial.|
|IIa||Evidence obtained from at least one well-designed controlled study without randomization.|
Evidence obtained from at least one other type of well-designed quasi-experimental study, without randomization.
|III||Evidence obtained from well-designed non-experimental descriptive studies, such as comparative studies, correlation studies, and case studies.|
|IV||Evidence obtained from expert committee reports or opinions and/or clinical experiences of respected authorities.|
Evidence obtained from qualitative inquiry was included throughout this guideline. Although recognized as important evidence that is “transformational” in its contribution to the nurse’s understanding of best practice, universally accepted strategy comparable to the systems developed for the interpretation of quantitative evidence do not yet exist (Sandelowski, 2004).