>
> The problem I have with these sorts of evidence hierarchies is that once
> you go below an RCT, how to prioritise? It seems to me that depending on
> the nature of the question posed, it may be that a cohort study with
> perhaps historical controls could actually be better than a sloppy
> case-control study where the controls were contemporaneous. And as we
> progress down the hierarchy, things seem to get murkier and
> murkier.............
>
> Or am I missing something?
>
> Paul
Paul
You are correct. There are levels of mid-level evidence (e.g. cohort vs.
case-control studies for the study of causation) that differ in their
potential for bias.
When seeking the best available evidence, in the absence of RCTs,
understanding this distinction is helpful.
When trying to determine if the evidence is "good enough to act on", then
many would argue to limit your evidence to high-quality RCTs.
So different philosophies (and different purposes) can lead to different
opinions over which level of evidence scheme is better.
Brian
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