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Eric Rasmusen's avatar

Thank you! Great article. I've made it a candidate for my Top Twelve of 2022.

The original idea of meta-analysis was that by combining many small studies, you'd have a big sample so statistically significant effects would have a chance to show up. Or, to not show up-- but you'd have higher power, more confidence that it wasn't just a small sample size that meant you got a null result.

In this homeopathy meta-study, though, what's happening is that the sixth study, the single-blind one has such a big effect that it's generating the entire result, it looks like to me-- even though it's being DILUTED, not ENHANCED, by the other studies. The purpose of a meta-study like this is just to camouflage the deficiencies of the one study that's generating the general conclusion from combining studies. Plus, you can claim that aggregating 6 studies produced result X, instead of just that one or two studies produced it, and other studies rejecting it. So the meta-analysis is just a rhetorical tool, a tool of obfuscation.

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Kevin McConway's avatar

Depressingly, though I hadn't looked at this particular meta-analysis, this matches many experiences I've had, in reviewing and in critiquing published papers. You have to check all or most of the papers that were included, maybe redo some of the calculations with dubious studies left out, and then you're still not sure because it takes too long to redo the literature search. Obviously there are some very good meta-analyses too, but meta-analyses are so much more demanding than other kinds of study to check for quality.

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