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Critical Appraisal Resources for Nursing Research and EBP

Levels of Evidence by Quantitative/Qualitative and Primary/Secondary Research

For further details on research design and levels of evidence, please refer to your nursing research/EBP textbook -

Schmidt, N.A., & Brown, J.M. (2019). Evidence-based practice for nurses (4th ed.). Jones & Bartlett: Burlington, MA

Finding a Study's Level of Evidence

If your study …

… then the most appropriate

JBI Checklist is:

Level of Evidence

Pro Tips

Is described as a Systematic Review and it reviews Randomized Controlled Trials. 

OR - 

Is described as a Meta-Analysis (a type of systematic review) and it analyzes data from several quantitative studies.  

Systematic Reviews Level I Systematic reviews can best be described as a study of other studies.  It's where the researchers systematically and rigorously review and analyze several studies on the same topic.  

Involves manipulation of an independent variable (intervention/treatment) to test its effect on a dependent variable (outcome), and the study participants are randomly assigned to one of two groups: experimental or control.  

 

Randomized Controlled Trial

 

Level II

Randomized controlled trials are often blinded, meaning that either the researchers or study participants (or both) are unaware of who is receiving the intervention and who is not.  This is important in reducing bias. 

Meets the criteria of one of these study design types: 

- Controlled trial with experimental and control groups, but without randomization (may have a pre-test/post-test or a post-test only)

- One-group (no control group), pre-test and post-test design without randomization

One-group post-test only design without randomization

One-group time series design without randomization

 

Quasi-Experimental

 

Level III

Please see Chapter 7.2 in your textbook (Schmidt & Brown, 2019, pp. 177-180) for full explanations of these various types of quasi-experimental studies. 

Compares the probability of developing a disease or condition among individuals who are exposed to a specific determinant versus those who are not exposed

 

Cohort

 

Level IV

A classic example of a cohort study is the comparison of those who smoke versus those who do not smoke, and the incidence of heart disease. 

 

Compares two groups of participants: those who have a disease/condition (“cases”) and those who do not (“controls”), in order to determine if there are any differences in characteristics or past exposures  

 

Case-Control

 

Level IV

Case-control studies are like cohort studies in reverse.  For example, a case-control study would compare individuals who already have heart disease, versus those who do not, and investigate past exposures.    

Analyzes relationships between an exposure and an outcome among a defined population at one point in time. 

Analytical Cross-Sectional

Level V

(Correlational)

An example of an analytical cross-sectional study would be a survey conducted over a 4-week period of adults in Ohio who participate in yoga (exposure) and whether it decreases their stress levels (outcome). 

Systematically reviews studies that are qualitative (sometimes these are called meta-syntheses).

OR -

Systematically reviews descriptive studies (not randomized controlled trials) 

Systematic Reviews

Level V

(Systematic reviews of qualitative studies OR Systematic reviews of descriptive studies)

If your study is a systematic review of randomized controlled trials, or a meta-analysis, then your level of evidence will be a I (see first row above).

If your study is a systematic review of only qualitative studies or only descriptive studies, then your level is a V.  

Uses participants’ words, language, and text as data rather than quantitative numbers and statistics.  Data is analyzed and coded thematically, not statistically. 

Qualitative

Level VI

Qualitative studies explore the “Why?” not the “What?” in order to increase our understanding of individuals’ perceptions and experiences. 

For further details on research design and levels of evidence, please refer to your textbook -

Schmidt, N.A., & Brown, J.M. (2019). Evidence-based practice for nurses (4th ed.). Jones & Bartlett: Burlington, MA