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Evidence-Based Practice

  Levels of Evidence

Levels of Evidence
are determined by the following:

1. Strength of Evidence: confidence that the evidence is a true measure

2. Quality of Evidence: minimization of bias

3. Statistical Precision: degree of certainty about the existence of a true measured effect

4. Size of Effect: how much of an effect is above 'No Apparent Effect' for clinically relevant benefits (no harms)

5. Relevance of Evidence: appropriateness of the outcome measure; usefulness in measuring benefits / harms

Highest Level of Evidence -- systematic review of all relevant randomized controlled trials (RCTs).

Next Highest Level of Evidence -- at least one RCT on effectiveness
And so on... e.g. a pseudo-randomized trial  that assigns participants by alternating between groups by date of admission

Lower Levels of Evidence --
    non-randomized studies with control group running concurrently with intervention group
    non-randomized studies with intervention effects which are compared to previous / historical information
    single-case studies

Confidence Interval (CI):
Covers the likely range of true effect. (play of chance can skew results)

Evidence Pyramid Example

Evidence Pyramid: Dartmouth & Yale

More Examples of EBM / EBP Pyramids

Take a look at the following websites that offer unique versions of the Evidence Pyramid.