Weaver et al developed the STOX (Systematic Reviews, Trials, Observational Studies, Expressions of Opinion) classification of evidence. The authors are from Cardiff University in Wales.
(1) systematic reviews (S)
(2) trials (T)
(3) observational studies (O)
(4) expressions of opinion (X)
comprehensive systematic review with >= 1 randomised controlled trial
comprehensive systematic review
randomised controlled trial
non-randomised controlled trial
interventional trial, before and after
cross sectional or longitudinal study
qualitative method only
formal consensus or other professional opinion
literature review without systematic approach
model based on reviews of the literature
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