Evidence · Meta-analyses · continued

Pooling trials with different estimands — what changed since posts 61–65

Evidence › Meta-analyses publication bias risk of bias meta-analysis effect size

This is a continuation of a long topic, addressed by post number rather than by page. Start at post 1.

retention_indexTL2Analytical chemist5 Dec 2025#61

d.vestergaard, post #41: Post #37 describes the usual case. This is about the unusual one. Pooled estimates and heterogeneity: when trials differ in population, duration, or comparator, a pooled estimate answers a question that no individual trial asked. High heterogeneity means effects genuinely differ across studies. The pooled number is an average of things… Go to post

Subgroup meta-analysis multiplies the usual subgroup problems by the number of included trials. Treat it as hypothesis-generating without exception.

11 likes in reply to #41 8mo

m.adeyemiTL27 Dec 2025#62

Fixed-effects versus random-effects models: fixed-effects assumes all studies are estimating the same thing and variation is sampling error. Random-effects assumes studies are estimating effects from different distributions and allows between-study variance. Choice matters if heterogeneity is high.

3 likes 8mo

chromatogramTL4Analytical chemist9 Dec 2025 · edited#63

Post #59 and I disagree about the size of the effect, not about the direction.

Fixed-effect and random-effects models answer different questions. The first assumes one true effect; the second assumes a distribution of them. Choosing between them is an assumption, not a technicality.

This is the version I would want a new member to read first.

0 likes 8mo

a.wikstromTL211 Dec 2025#64

Taking post #63 at face value and following it one step further.

The failure mode on Pooling trials with different estimands is boring rather than dramatic. It is almost always the step everyone assumes was done correctly because it is too simple to get wrong.

24 likes 8mo

appeals_deskTL3Regular13 Dec 2025#65

n.vukovic, post #51: Narrowing post #48, because the general version has more than one answer. Practical note on Pooling trials with different estimands: write down what you expect before you look. The number of times I have found what I went looking for is higher than chance would allow. Go to post

Same experience here, different supplier, so it is at least not unique to one of them.

16 likes in reply to #51 7mo

This topic was referenced in

When a network meta-analysis is defensible and when it is notEvidence › Meta-analyses · 2 replies

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