This is a continuation of a long topic, addressed by post number rather than by page. Start at post 1.
Worth separating two things that post #59 runs together.
Screening on a preprint server is minimal and is not review. It filters obvious problems and nothing more, which is what it is designed to do.
The strength of my opinion here exceeds the strength of my evidence.
Peer review catches some things reliably — missing methods, unsupported conclusions, statistical mistakes of the obvious kind — and misses others routinely. Knowing which is which makes preprint reading easier.
Author track record is a weak signal and it is a signal. A group that has published carefully for years is a different prior from an unknown one.
Flagging that the sources on this are thinner than the confidence in the thread suggests.
Post #63 answers the question as asked. The question underneath it is different.
Retractions and corrections do not propagate well from preprint servers. A citation that was fine when made can quietly become wrong.
The number is defensible. The precision I gave it is not.
On post #63 — agreed on the reasoning, with one qualification.
Preprint servers 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.
I read the earlier replies on preprint servers twice before writing this, because I had assumed the opposite and wanted to be sure I was disagreeing with what was said rather than what I expected.
Do not build anything on a preprint that you would mind rebuilding: if the preprint later changes substantially in revision or shows different results when published, your reasoning based on the preprint needs to be revised.
Post #67 is right about the mechanism and I think understates the practical bit.
Always label it as a preprint in any discussion. A preprint is not a published trial and it is not settled knowledge. Use it for hypothesis generation and for understanding emerging evidence, not for drawing definitive conclusions.
Post #67 put the caveat in the right place and I want to underline it.
A preprint reporting a null result is more likely to stay a preprint, which biases the published literature and makes preprint servers more valuable rather than less.
Right, and stated more narrowly than I would have dared to state it.
If you cite a preprint in a maintained document here, the convention is to label it in the sentence and to note the check date. The document review will catch the update.
Second-hand, so weight it accordingly.
Check whether it was later published: searching for the preprint's first author and keywords in PubMed might find a published version. The published version is the stronger citation if it exists.
Posting it because the silence on this was starting to look like agreement.
Post #71 is the version of this I will quote in future. One addition.
How to cite a preprint: author last name, first initial, et al. Title. Server name [preprint]. Posted date. Doi. Include the server name and note that it is a preprint.
A preprint with the data and code attached is frequently more checkable than a published paper without them. Reviewed and reproducible are different properties.
Confirming post #74 from a second method, which matters more than confirming it from a second person.
Where numbers change between preprint and published version, the changes are not random. They tend toward a smaller effect and a more carefully hedged claim.
Adding it because I spent an afternoon working it out and nobody should have to twice.
I had written a reply contradicting post #77 and deleted it. Here is what survived.
Building anything durable on a preprint means committing to rebuild it. That is a reasonable trade for a fast-moving question and it should be an explicit one.
This follows post #78 rather than contradicting it.
Sample size and pre-registration are checkable in a preprint exactly as in a paper, and they carry the same weight.
Worth separating two things that post #77 runs together.
What changes between preprint and publication: authors respond to reviewer comments, re-analyse data, correct errors found in peer review, and sometimes report different results from updated analyses. The published version is not the same as the preprint.
Whatever the answer on preprint servers turns out to be, the method for getting there is the same: state the assumption, do the arithmetic in public, invite the correction.
Server repositories: medRxiv for medicine, bioRxiv for biology. Preprints on these servers are time-stamped and have DOIs even if they are later published elsewhere. Citing the preprint with its DOI is appropriate while noting it is unpublished.
This is where my knowledge stops and I would rather mark the edge than blur it.
Helpful, and short, which on this subject is harder than long.
Building on post #81 rather than restating it.
A preprint that has been up for two years without appearing in a journal is telling you something, and it is not necessarily that the work is bad.
I have seen it go both ways, which is why I hedge.
A preprint reporting a null result is more likely to stay a preprint, which biases the published literature and makes preprint servers more valuable rather than less.
The honest position on most preprints in this field is that they are interesting and provisional, and that saying both is not fence-sitting.
That is all the detail I have. Someone else will have more.