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DNP Evidence-Based Practice Project: Library Resources: Critical Appraisal and Levels of Evidence

This guide is designed to assist graduate students in the Doctor of Nursing Practice (DNP) program with the research and scholarly writing components of the final DNP Project.

Recommended Books

Critical Appraisal Tools

A variety of critical appraisal tools are available from different organizations.

The following links will connect you to these tools. 

PLEASE NOTE: If you are using a specific EBP implementation model for your project, that model may have its own set of appraisal tools and techniques (and levels of evidence), so be sure to use those for your DNP project. 

Levels of Evidence

What are Levels of Evidence? 

  • In evidence-based practice, individual research studies are ranked and assigned levels of evidence based on their methodological strength
  • Study designs with the least potential risk for bias are at the top of the evidence hierarchy
  • Study designs with greater risk for bias are ranked lower
  • There are several variations of evidence hierarchy models. In most of these hierarchies, systematic reviews of randomized controlled trials are ranked highest, with expert opinion ranked lowest. 
  • Evidence levels are primarily an indicator of potential risk for bias being present in the study results, with the least risk for bias at the top and higher risk for bias at the bottom


Guyatt G. Rennie D. Meade M. Cook D. & American Medical Association. (2015). Users' guides to the medical literature: A manual for evidence-based clinical practice (3rd ed.). McGraw-Hill Education.

Melynk & Fineout-Overholt Levels of Evidence

In the DNP program, the levels of evidence developed by Melnyk & Fineout-Overholt are the most widely used and applied. 

Level 1: Systematic review & meta-analysis of randomized controlled trials; clinical guidelines based on systematic reviews or meta-analyses

Level 2: Randomized controlled trial

Level 3: Controlled trial (no randomization) [note: these include quasi-experimental studies]

Level 4: Case-control or cohort study

Level 5: Systematic review of descriptive & qualitative studies

Level 6: Single descriptive or qualitative study

Level 7: Expert opinion