The Health Evidence Bulletins Wales classification of evidence type
| Type of evidence | Example |
|---|---|
| Type I evidence | At least one good systematic review (including at least one randomised controlled trial) |
| Type II evidence | At least one good randomised controlled trial |
| Type III evidence | A well designed interventional study without randomisation |
| Type IV evidence | A well designed observational study |
| Type V evidence | Expert opinion; influential reports and studies |