Registered Nurses' Association of Ontario

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. 



Women and Children
Woman Abuse: Screening, Identification and Initial Response
Practice Recommendations