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Research Methods · Statistics · continued

Measurement error in home scales, with a worked standard deviation — the long version posts 61–90

This is a continuation of a long topic, addressed by post number rather than by page. Start at post 1 · go to the accepted answer.

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c.correiaTL225 Mar 2026#61
d.yilmaz, post #4: Confounding: a third variable explains an apparent association. In randomised data, randomisation balances confounders. In observational data, confounders can be adjusted for but unknown ones cannot. I have kept the units in throughout, for the obvious reason. Go to post

Baseline imbalance in a randomised trial is expected by chance and adjusting for it post hoc is a choice that should have been pre-specified.

Worth saying I have only my own numbers here, and n is small.

0 likes in reply to #4 4mo
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me.eriksenTL226 Mar 2026#62

Useful. I have added it to my own notes with the date on it.

1 like 4mo
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m.lehtinenTL227 Mar 2026#63

Where I have landed on Measurement error in home scales, having got it wrong once in public: the direction is clear, the magnitude is not, and anyone quoting a precise magnitude has borrowed it from somewhere that did not measure it.

7 likes 4mo
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c.cardosoTL228 Mar 2026#64
IHollingworth, post #46: Whatever the answer on Measurement error in home scales turns out to be, the method for getting there is the same: state the assumption, do the arithmetic in public, invite the correction. Go to post

Relative risk and odds ratios: both compare the rate in one group to the rate in another. Relative risk is easier to understand. Odds ratios are standard in many analyses but can be misinterpreted.

Stating my assumptions rather than smuggling them in.

18 likes in reply to #46 4mo
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f.sjobergTL230 Mar 2026#65
c.correia, post #61: Baseline imbalance in a randomised trial is expected by chance and adjusting for it post hoc is a choice that should have been pre-specified. Worth saying I have only my own numbers here, and n is small. Go to post

Answering the Measurement error in home scales question as asked, then the question I think is meant. As asked: yes, with the qualification below. As meant: it depends on how the first measurement was taken.

0 likes in reply to #61 4mo
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dr_okonkwoTL4 Moderator31 Mar 2026#66

A standard deviation describes the spread of individuals and a standard error describes the precision of the mean. Quoting one where the other belongs changes the apparent result substantially.

Take it as a starting point and not as a specification.

4 likes 4mo
MP
m.perrinTL21 Apr 2026 · edited#67

Adding the measurement that post #64 says would settle it.

I would put moderate confidence on the mainstream reading of Measurement error in home scales and no more. That is not scepticism for its own sake; it is where the sourcing actually stops.

12 likes 4mo
SK
s.karlsen_rphTL3Pharmacist2 Apr 2026#68

On Measurement error in home scales: the maintained page in the documentation commons covers the general case with citations and a review date, which is more reliable than any reply here including this one.

25 likes 4mo
CW
cohort_watchTL2Member3 Apr 2026#69
policy_reader, post #19: Relative risk and odds ratios: both compare the rate in one group to the rate in another. Relative risk is easier to understand. Odds ratios are standard in many analyses but can be misinterpreted. The variance between people here is larger than the effect being discussed. Go to post

Same experience here, different supplier, so it is at least not unique to one of them.

1 like in reply to #19 4mo
RM
ra.mensaTL25 Apr 2026#70
br.wikstrom, post #34: Taking post #33 at face value and following it one step further. The useful distinction on Measurement error in home scales is between what was measured and what was inferred from it. Both end up in the same sentence and only one of them has error bars. Go to post

Percentages of small denominators should be reported with the denominator. Two out of three is not sixty-seven per cent in any useful sense.

I would treat that as a working assumption and revisit it.

7 likes in reply to #34 4mo
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s.adebayoTL26 Apr 2026#71
f.sjoberg, post #65: Answering the Measurement error in home scales question as asked, then the question I think is meant. As asked: yes, with the qualification below. As meant: it depends on how the first measurement was taken. Go to post

Coming back to post #70, because the follow-up matters more than the original answer.

Where an analysis was changed after seeing the data, the honest thing is to report both and say which was pre-specified.

10 likes in reply to #65 4mo
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formulary_notesTL3Regular7 Apr 2026#72

Seconded. It reads as careful rather than confident, which is the right register.

3 likes 4mo
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c.amankwahTL28 Apr 2026#73

Adding a null result on Measurement error in home scales. I looked, carefully, and found nothing, and null results deserve posting precisely because they never are.

0 likes 4mo
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TL4_HalvorsenTL4Leader · Journal club9 Apr 2026 · edited#74

This follows post #73 rather than contradicting it.

Confidence intervals: rather than a single point estimate, a range of plausible values. A narrow interval means precise measurement; a wide interval means measurement is imprecise. Wider intervals (more uncertainty) are honest about limitation.

31 likes 4mo
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i.ilungaTL211 Apr 2026#75
c.correia, post #61: Baseline imbalance in a randomised trial is expected by chance and adjusting for it post hoc is a choice that should have been pre-specified. Worth saying I have only my own numbers here, and n is small. Go to post

I had written a reply contradicting post #73 and deleted it. Here is what survived.

Measurement error in home scales sits at the boundary between what this community can usefully discuss and what it cannot, and I think it falls on the discussable side, narrowly.

15 likes in reply to #61 4mo
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sleep_logTL2Regular12 Apr 2026#76
n.ramos, post #45: Building on post #42 rather than restating it. On Measurement error in home scales, I would rather understate and be corrected upward than overstate and be quoted. That is a house style here and it is a good one. Go to post

Confirming post #73 from a second method, which matters more than confirming it from a second person.

Trying to state the Measurement error in home scales position in a way that someone who disagrees would recognise as fair, because I do not think the version in this thread passes that test.

6 likes in reply to #45 4mo
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l.vukovicTL213 Apr 2026#77

Rounding and significant figures carry information about precision. A figure quoted to four significant figures from a method with two per cent variability is overstating what is known.

The confident version of this sentence would be wrong, so here is the hedged one.

1 like 3mo
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weekly_pinTL2Regular14 Apr 2026#78

An update on my earlier Measurement error in home scales post: the pattern held for another six weeks and then stopped, which I did not predict and cannot explain.

0 likes 3mo
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m.ibarraTL215 Apr 2026#79

This settles it for me, at least until somebody posts a reason it should not.

22 likes 3mo
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s.leclercTL4 Moderator17 Apr 2026#80

Narrowing post #77, because the general version has more than one answer.

Confidence intervals: rather than a single point estimate, a range of plausible values. A narrow interval means precise measurement; a wide interval means measurement is imprecise. Wider intervals (more uncertainty) are honest about limitation.

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

10 likes 3mo
AP
a.pereiraTL218 Apr 2026#81
v.kirchner, post #60: Post #59 is the version of this I will quote in future. One addition. If you are new and reading this thread for the answer to Measurement error in home scales: the answer is conditional, the conditions are in the third reply, and the rest of the thread is worth skipping. Go to post

My position on Measurement error in home scales is current rather than settled. I have revised it once already and I expect to again, so treat it accordingly.

1 like in reply to #60 3mo
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forest_plotTL3Evidence synthesis19 Apr 2026#82
m.ibarra, post #79: This settles it for me, at least until somebody posts a reason it should not. Go to post

Offering a way to settle Measurement error in home scales rather than another opinion about it. Two measurements, taken the same way, a fortnight apart. If the difference is within the noise, the question was not answerable at this precision.

6 likes in reply to #79 3mo
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h.bakkerTL220 Apr 2026#83

Confounding: a third variable explains an apparent association. In randomised data, randomisation balances confounders. In observational data, confounders can be adjusted for but unknown ones cannot.

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

22 likes 3mo
PE
ppm_errorTL3Analytical chemist21 Apr 2026#84

Answering the question post #80 raises rather than the one it answers.

A p-value is the probability of data at least this extreme given the null hypothesis. It is not the probability the hypothesis is false, and almost every plain-language gloss gets that backwards.

Two sources, same conclusion, and I could not rule out that one copied the other.

0 likes 3mo
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r.lundgrenTL222 Apr 2026#85

Second-hand on Measurement error in home scales, so weight it accordingly — someone whose method I trust told me this and I have not verified it myself.

0 likes 3mo
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d.moreauTL2Regular23 Apr 2026#86
c.falk, post #6: Where the Measurement error in home scales discussion usually stalls is that nobody wants to say "I do not know" and everyone is willing to say "it varies". Those are the same sentence with different clothes on. Go to post

The bit of Measurement error in home scales that nobody enjoys is that the answer changes depending on what you are trying to decide with it. Say what the decision is and the thread will converge.

3 likes in reply to #6 3mo
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n.cardosoTL225 Apr 2026 · edited#87

I will take the caveat as seriously as the claim, which is the point of putting it there.

16 likes 3mo
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o.lindgrenTL2Regular26 Apr 2026#88

Post #84 describes the usual case. This is about the unusual one.

Effect sizes: the magnitude of a difference, not just whether it is statistically significant. A difference that is significant (p<0.05) might be too small to matter. A large effect might not be significant if sample size is small.

Reading it back, the second half matters more than the first.

31 likes 3mo
MA
m.almeidaTL227 Apr 2026#89
r.sobczak, post #47: Confidence intervals: rather than a single point estimate, a range of plausible values. A narrow interval means precise measurement; a wide interval means measurement is imprecise. Wider intervals (more uncertainty) are honest about limitation. Go to post

This follows post #86 rather than contradicting it.

Survivorship in a self-reporting population biases every aggregate produced from it, and the bias is in the flattering direction.

The uncertainty is in the assumption, not in the calculation.

0 likes in reply to #47 3mo
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k.brandl_deTL3Translator · DE28 Apr 2026 · edited#90

Worth separating two things that post #88 runs together.

Reframing Measurement error in home scales slightly, because I think the disagreement is about the question rather than the answer. If the question is "does it happen", yes. If it is "how often", nobody here knows.

1 like 3mo