When meta-analysis goes wrong

Stuart Ritchie in Science Fictions:

Six years ago, the psychologist Michael Inzlicht told Slate magazine that “meta-analyses are fucked”.

It’s always stuck with me – the clash between that statement and how we’re meant to feel about meta-analyses. They’re supposed to be the highest form of evidence – a systematic review of all the studies on a particular scientific question, followed by a quantitative estimate of where the evidence points as a whole. No mere opinions, like in a narrative “review” article; no reliance on a single study. A meta-analysis tells us what we really want to know.

And indeed, if you roll out a meta-analysis in a debate over some scientific matter, it’s a powerful finishing move. That’s why those strange advocacy groups for ivermectin and hydroxychloroquine set up those (dodgy) meta-analysis websites during the pandemic – they knew the power of being able to say “meta-analytically, the evidence supports my view”.

And yet meta-analyses are fucked.

More here.