Topic summary

Random versus fixed effects: choosing rather than defaulting — a second dataset

Evidence › Meta-analyses heterogeneity risk of bias publication bias

This is a generated summary. It shows the 9 most-liked posts from a topic of 107, in their original order, with the accepted answer included where one exists. It is a reading aid and it will miss nuance — the full topic is the record.

buffer_shiftTL1Member24 Jan 2025#4

st.diallo, post #3: Where the pooled result and the largest single trial disagree, that disagreement is the interesting thing rather than an inconvenience to be smoothed. I would rather be precise about what I do not know than vague about what I do. Go to post

Study quality and weighting: some meta-analyses weight all studies equally; others weight by study size or study quality. The choice affects the result and should be stated and justified.

Filing this under things that are true until someone shows me otherwise.

27 likes in reply to #3 18mo

GEldridgeTL3Regular27 Jan 2025#12

Building on post #11 rather than restating it.

Quality assessment of included trials should change the analysis rather than sit beside it. A sensitivity analysis excluding the weakest studies is the minimum.

Worth one more sentence than it usually gets.

27 likes 18mo

ca.vermeulenTL228 Jan 2025#19

Worth separating two things that post #15 runs together.

A definition problem is doing most of the work in this Random versus fixed effects discussion. Once the term is pinned down I suspect the disagreement mostly goes away and what is left is small.

28 likes 18mo

i.oseiTL231 Jan 2025#32

Building on post #29 rather than restating it.

On Random versus fixed effects, the part that usually goes wrong is that the question is asked as though it has one answer. It has a range, and the width of the range is the interesting bit.

If you can post the two or three numbers you are working from, several people here will check the arithmetic rather than argue about the conclusion.

32 likes 18mo

vial_deskTL3Regular3 Feb 2025#48

z.szabo, post #28: Funnel plots: a plot of study effect size versus sample size that helps detect publication bias. If small studies are missing on the negative side, the funnel is asymmetrical. I would call that likely rather than established. Go to post

Individual participant data pooling is a much stronger design than aggregate pooling and is rare because it requires cooperation rather than a search.

30 likes in reply to #28 18mo

k.dahlbergTL26 Feb 2025#64

Quality assessment of included trials should change the analysis rather than sit beside it. A sensitivity analysis excluding the weakest studies is the minimum.

32 likes 18mo

i.balogunTL27 Feb 2025#72

Picking up post #69: that is the part I would want checked first.

Worth separating Random versus fixed effects as a question about the compound from Random versus fixed effects as a question about the documentation. They get answered by different people and only one of them is answerable here.

30 likes 18mo

IRenaudinTL2Member9 Feb 2025#79

b.teixeira, post #38: Adding the measurement that post #37 says would settle it. 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… Go to post

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.

31 likes in reply to #38 18mo

ai.vukovicTL210 Feb 2025#85

b.osei, post #62: Post #58 describes the usual case. This is about the unusual one. Random versus fixed effects came up in a thread eighteen months ago and was answered well. I cannot find it, which is itself the problem, so here is the reconstruction. Go to post

Post #82 answers the question as asked. The question underneath it is different.

Where the Random versus fixed effects reasoning breaks down for me is the step from the group result to the individual case. That step is almost never argued for.

29 likes in reply to #62 18mo

Read the full topic (107 posts)

Moved from Preprints by s.leclerc. Category placement is not obvious from outside and getting it wrong is expected. This topic will get better answers here. The move is recorded in the public log citing R7.

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