Evidence · Trials

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Evidence › Trials randomised trial estimand intention to treat

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j.mwangiTL4 Moderator11 Jul 2025#1

Community wiki post. Any member at trust level 3 or above can edit this post; every edit is recorded. Last edited by hana.sato on 22 Jan 2026.

28 Jul 2025 — j.mwangi: Plain-language pass on the opening paragraph.
26 Dec 2025 — mira.patel: Corrected an arithmetic slip in the second example.
22 Jan 2026 — hana.sato: Added the limitations paragraph that review asked for.

Editors: j.mwangi, mira.patel, hana.sato

Staff post. Actions described here are recorded in the public moderation log and may be challenged in Meta.

Individual randomised trials: design, population, endpoints, results, and limitations.

This post is a community wiki: any member at trust level 3 or above can edit it, and every edit is recorded with its author and a note. If the scope described here has drifted from what actually gets posted, edit it rather than starting a topic about it.

What belongs here

Questions specific to trials, with the units and the context stated.
Reports and datasets, with the collection method stated.
Disagreement about the substance, conducted in public.

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Anything urgent belongs in Safety, immediately, and not here.
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Before posting, it is worth checking the documentation commons and this category's tag pages. A great deal of what gets asked here has a maintained answer with a review date on it, which is more reliable than a two-year-old reply.

53 likes 13mo

bench_notesTL4 Moderator12 Jul 2025#2

Staff post. Actions described here are recorded in the public moderation log and may be challenged in Meta.

Moderation notes for this category, so that nothing about how it is run is a surprise.

Topics get moved into and out of here regularly. A move is not a judgement — the category tree is not obvious from outside and putting a question in the wrong place is expected. When I move something I say so in the topic and the action appears in the public log with the guideline cited.

The two guidelines that come up most often in this category are R2, on supplying a source when asked, and R7, on category placement. Neither is used punitively.

14 likes 13mo

system_suitabilityTL3Analytical chemist13 Jul 2025#3

As a member rather than staff: the most useful thing I did when I started reading this category was to work through the tag pages rather than the topic list. The topic list shows you what is recent. The tags show you what is settled.

5 likes 12mo

z.okonkwoTL215 Jul 2025#4

Suggestion for the wiki post above: it would be worth linking the two or three most-referenced topics in this category directly, since new members reliably ask for exactly those. Happy to make the edit myself if nobody objects, with a revision note.

0 likes 12mo

e.mwangiTL216 Jul 2025#5

Collapsed as off-topic by two members at trust level 3 or above

A treatment-policy estimand asks what happens to people assigned to a strategy, including those who abandon it. A hypothetical estimand asks what would have happened had everyone continued. Both are legitimate and they give different numbers.

trough_indexTL3Regular16 Jul 2025#6

bench_notes, post #2: Moderation notes for this category, so that nothing about how it is run is a surprise. Topics get moved into and out of here regularly. A move is not a judgement — the category tree is not obvious from outside and putting a question in the wrong place is expected. When I move something I say so in the topic and the action appears in the… Go to post

Risk of bias: structured appraisal of internal validity. Key things to assess: randomisation method (was it truly random or could someone predict the next assignment), concealment (could randomisation be subverted), blinding (who was blinded and why or why not), completeness of outcome reporting.

I would want a second opinion before relying on that.

9 likes in reply to #2 12mo

a.norgaardTL217 Jul 2025#7

Open-label design: unblinded trials admit expectation effects. For weight-loss trials where one arm loses substantial weight and the other does not, complete blinding is impossible anyway. The unblinded nature is a limitation worth noting.

Someone will know this better than I do and I hope they say so.

2 likes 12mo

n.bridgewaterTL2Member18 Jul 2025#8

That is clearer than the version I had in my head. Thank you.

0 likes 12mo

h.kimaniTL219 Jul 2025#9

On post #7 — agreed on the reasoning, with one qualification.

The estimand: what the trial set out to estimate. Two trials can be identical in structure but estimate different things by using different handling rules for people who stop taking the drug. Treatment-policy and hypothetical approaches are both legitimate but answer different questions.

0 likes in reply to #2 12mo

BDraganovTL2Member20 Jul 2025#10

Picking up post #7: that is the part I would want checked first.

Absolute and relative effects answer different questions. Write down the event rate in each arm and the difference between them; everything quotable is derived from those two numbers.

28 likes 12mo

sa.okonkwoTL221 Jul 2025#11

Population narrowness: most trials in this class enrolled fairly specific groups. Baseline body mass index ranges, exclusion of renal disease, exclusion of certain comorbidities, all narrow the population. Applying point estimates to someone well outside the range is an extrapolation.

12 likes 12mo

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