On the subject in the title: Pooling trials with different estimands Working notes rather than a conclusion.
Asking about pooling trials with different estimands on behalf of the question I keep seeing asked badly, including by me.
Framed properly it is answerable. Framed the usual way it is not, and that is most of why the previous threads went nowhere.
Taking pooling trials with different estimands seriously for a moment rather than deflecting: the honest position is that the community has observations and no controlled comparison, and those two things support very different sentences.
I had written a reply contradicting post #11 and deleted it. Here is what survived.
Whatever the answer on pooling trials with different estimands turns out to be, the method for getting there is the same: state the assumption, do the arithmetic in public, invite the correction.
This follows post #38 rather than contradicting it.
Before the thread moves on from pooling trials with different estimands — what is the sample size behind the claim? I am not being difficult; I have seen the same figure quoted from an n of four and from an n of four hundred.
Where I part company with post #53, and it is a narrow parting.
When trials differ in population, duration and comparator, the pooled estimate answers a question no individual trial asked. That is worth saying before the number is quoted.
Happy to expand any of that if it is the useful part.
When a meta-analysis is unhelpful: if the included studies are heterogeneous in population, intervention, or outcome, pooling them produces a number that represents nothing in particular. Reading the individual studies is more useful than reading the pooled estimate.
Taking post #68 at face value and following it one step further.
An observation about pooling trials with different estimands that I cannot explain and am posting anyway, on the principle that unexplained observations are more useful public than private.
The arithmetic in post #95 is right; the assumption feeding it is the part to check.
The arithmetic on pooling trials with different estimands is the easy part and it is where the errors are, which is an uncomfortable combination. Show your working and someone will catch it.
Read the full topic (133 posts)
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