Understanding Nursing

The strength or validity of the best research evidence in an area depends on the quality and quantity of the studies that have been conducted in regards to that area. Quantitative studies provide the strongest research evidence.

Systematic research reviews and meta-analyses of high quality, experimental studies provide the strongest or best research evidence used by expert clinicians in practice to determine best evidence-based practice. The weakest evidence comes from expert opinions, which can include expert clinicians’ opinions, or the opinions expressed in committee reports.

The levels of best research evidence listed from strongest to weakest are:

  1. Systematic review of experimental studies
  2. Meta-analysis of experimental, quasi-experimental and outcomes studies
  3. Integrative reviews of experimental, quasi-experimental and outcomes studies
  4. Single experimental study
  5. Single quasi-experimental study
  6. Meta-analysis of correlational studies
  7. Integrative reviews of correlational and descriptive studies
  8. Qualitative research meta-synthesis and meta-summaries
  9. Single correlational study
  10. Single qualitative or descriptive study
  11. Opinions of respected authorities based on clinical evidence, reports of expert committees


Grove, S., Gray, J., & Burns, N. (2015). Understanding Nursing Research: Building an Evidence Based Practice. Retrieved from https://pageburstls.elsevier.com/#/books/978145577…

Last Updated on February 11, 2019

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