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Data & Tools · Datasets · continued

Aggregated purity results across four services, with caveats — a second dataset posts 91–120

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

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au.pereiraTL29 Sep 2025 · edited#91

Aggregating first-hand accounts does not produce evidence of the kind a trial produces. It produces a description of who chose to post, which is a real thing and a different thing.

Posting it because the silence on this was starting to look like agreement.

2 likes 11mo
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maintenance_modeTL3Regular9 Sep 2025#92

Where I part company with post #91, and it is a narrow parting.

Two questions I would want answered before drawing anything from the Aggregated purity results across four data above: how were the cases selected, and what happened to the ones that dropped out.

8 likes 11mo
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a.ilungaTL210 Sep 2025#93

Adding the measurement that post #92 says would settle it.

Temporal bias: older data in a dataset might reflect conditions (supplier, formulation, context) that have changed. Newer data is more current.

19 likes 11mo
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logbook_erinTL3Regular10 Sep 2025#94
m.ekstrom, post #56: Post #54 describes the usual case. This is about the unusual one. The documentation on Aggregated purity results across four is better than this thread and I say that as someone who has posted in the thread. Go to post

Aggregated purity results across four: I have looked for the primary source twice and failed twice. Either it does not exist or it is somewhere I do not know to look, and I would like to know which.

0 likes in reply to #56 11mo
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p.krastevTL210 Sep 2025#95

Aggregated purity results across four looks different depending on whether you are reading the primary literature or the summaries of it, and the difference is not in our favour.

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isotonic_sheetTL3Regular10 Sep 2025#96

Units in the column header, always, and the same units down the whole column. Mixed units in one field is the commonest defect in shared spreadsheets here.

A guess, clearly labelled as one.

12 likes 11mo
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f.danquahTL210 Sep 2025#97
t.tulloch, post #26: Post #23 answers the question as asked. The question underneath it is different. Nobody has said the unglamorous part of Aggregated purity results across four yet, so: most of the variation is explained by things that are boring to write about and easy to check. Go to post

Appreciated. The plain phrasing does more work here than a longer post would.

26 likes in reply to #26 11mo
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r.venkatesanTL3Wiki editor10 Sep 2025#98
crossover_review, post #48: Post #45 is right about the mechanism and I think understates the practical bit. Temporal bias: older data in a dataset might reflect conditions (supplier, formulation, context) that have changed. Newer data is more current. If that reads as pedantic, it is, and it has saved me twice. Go to post

Answering the question post #94 raises rather than the one it answers.

Sample size is not the only thing that determines what a dataset can support. Selection is usually the larger problem here and it does not improve with volume.

Second-hand, so weight it accordingly.

0 likes in reply to #48 11mo
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h.vargaTL210 Sep 2025#99

Post #96 is right about the mechanism and I think understates the practical bit.

How to contribute: if you have longitudinal data you want to add, the format is simple: date, measurement, context. Contact the maintainer of the specific dataset.

0 likes 11mo
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v.szaboTL3Analytical chemist10 Sep 2025 · edited#100

I have been on both sides of the Aggregated purity results across four argument in this category within eighteen months, which should tell you how strong the evidence for either side is.

2 likes 11mo
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j.silvaTL210 Sep 2025#101
Thibodeau, post #57: Confirming post #56 from a second method, which matters more than confirming it from a second person. The arithmetic on Aggregated purity results across four is the easy part and it is where the errors are, which is an uncomfortable combination. Show your working and someone will catch it. Go to post

Narrowing post #98, because the general version has more than one answer.

Combining results from different testing services into one column loses information that matters. Keep the service as a field.

Reading it again, the caveat matters more than the finding.

0 likes in reply to #57 11mo
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m.stephanopoulosTL3Regular10 Sep 2025#102

Everything in post #100 holds. The case it does not cover is the one I have.

The most useful dataset this community could hold is boring: lot, supplier, service, method, date, result. That is enough to answer most of the questions people ask badly.

It is worth checking rather than assuming, which costs nothing.

0 likes 11mo
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h.nwosuTL210 Sep 2025 · edited#103

Since Aggregated purity results across four keeps coming up, it should probably be a maintained page rather than a recurring thread. I am happy to draft it if someone with more direct experience will review it.

7 likes 11mo
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OstrowskiTL2Member10 Sep 2025#104
vial_desk, post #25: My experience of Aggregated purity results across four contradicts the reply above. I am posting it as a data point rather than as a refutation, because one person's experience is exactly that. Go to post

The most useful reply I ever got about Aggregated purity results across four was a request to state my units. It sounds like pedantry and it has saved me twice.

18 likes in reply to #25 11mo
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w.moreauTL210 Sep 2025#105
crossover_review, post #48: Post #45 is right about the mechanism and I think understates the practical bit. Temporal bias: older data in a dataset might reflect conditions (supplier, formulation, context) that have changed. Newer data is more current. If that reads as pedantic, it is, and it has saved me twice. Go to post

Where a value is derived rather than measured, mark it. Derived columns get treated as observations the moment the file leaves your hands.

0 likes in reply to #48 11mo
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taper_shiftTL3Regular10 Sep 2025#106

I read post #104 twice before replying, because I had assumed the opposite.

Independent test results are the most valuable data this community collects, and they are only comparable when the method is captured alongside the number.

I would hold that lightly until someone with a larger sample weighs in.

1 like 11mo
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so.mbekiTL210 Sep 2025#107

Date every record. A dataset assembled over two years without dates cannot distinguish a change over time from a change in who was contributing.

The answer changed when I changed how I was measuring, which was informative.

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FFaulknerTL3Regular10 Sep 2025#108

This is the answer, and the reason it is the answer is the more useful part.

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a.adebayoTL210 Sep 2025#109
j.habermann, post #84: Publishing the raw records alongside the summary is what makes a dataset checkable. A summary alone asks for trust that nobody has earned. Go to post

Aggregated purity results across four has a well-known answer and a correct answer, and the interesting work is establishing that they are the same. Nobody has done that here yet.

19 likes in reply to #84 11mo
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r.laurentTL210 Sep 2025#110
a.adebayo, post #109: Aggregated purity results across four has a well-known answer and a correct answer, and the interesting work is establishing that they are the same. Nobody has done that here yet. Go to post

Adding what did not work for me on Aggregated purity results across four, since the failures never get written up and they are half the useful information.

0 likes in reply to #109 11mo
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system_suitabilityTL3Analytical chemist10 Sep 2025#111

Answering the question post #107 raises rather than the one it answers.

Version the file rather than editing in place. A dataset that changes silently under an analysis makes the analysis unreproducible.

This has been discussed before and I could not find the thread, so, again.

24 likes 11mo
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h.iyerTL210 Sep 2025#112

The arithmetic in post #111 is right; the assumption feeding it is the part to check.

Aggregated purity results across four was covered in the wiki last year and the page has a review date on it, which is a better starting point than my memory of a thread.

11 likes 11mo
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k.otieno_statsTL3Statistician10 Sep 2025#113
system_suitability, post #111: Answering the question post #107 raises rather than the one it answers. Version the file rather than editing in place. A dataset that changes silently under an analysis makes the analysis unreproducible. This has been discussed before and I could not find the thread, so, again. Go to post

Bookmarking this. I will come back when I have something worth adding.

1 like in reply to #111 11mo
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n.ibarraTL210 Sep 2025#114
c.balogun, post #87: If you are new and reading this thread for the answer to Aggregated purity results across four: the answer is conditional, the conditions are in the third reply, and the rest of the thread is worth skipping. Go to post

Reading this Aggregated purity results across four thread as someone who came in with a fixed view: the third and seventh replies moved me and the confident ones did not.

0 likes in reply to #87 11mo
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q.zhao_qaTL3Quality assurance10 Sep 2025#115

Aggregating first-hand accounts does not produce evidence of the kind a trial produces. It produces a description of who chose to post, which is a real thing and a different thing.

Not disagreeing with anyone above, just adding the bit I keep having to look up.

17 likes 11mo
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e.steinerTL210 Sep 2025#116

Narrowing post #115, because the general version has more than one answer.

A codebook describing each field takes twenty minutes and is what makes the file usable by anyone but you. Most shared datasets here do not have one.

It is worth stating the boring hypothesis before the interesting one.

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unit_conversionTL3Regular10 Sep 2025#117

Aggregated purity results across four is a good example of a question where the honest answer is boring and the interesting answers are unsupported. I would go with boring.

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i.lehtinenTL210 Sep 2025#118
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f.wojcikTL210 Sep 2025#119
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s.rasmussenTL210 Sep 2025#120

Two sentences on Aggregated purity results across four and then I will stop, because the rest is speculation and the thread is better without mine.

What is documented is narrow. What is inferred from it is broad. The gap between them is where every argument here lives.

23 likes 11mo