daniel added a comment.
@Jc3s5h Well, if we have additional information about the methods and tools
used for the measurement, we should use them, sure. The source should state
them, and we should record them. That's the simple case.
But the question we are trying to answer here is what to use if we have no such
information. All we have to go by is a decimal string, and some inconclusive
conventions about significant digits. So, what's the best for our primary use
case, namely //rounding after unit conversion//? We could
1. assume +/-0: This will introduce spurious digits (false precision), because
it prevents any rounding to be applied.
2. assume +/-1: This is inconsistent with the rounding algorithm we apply
("round half away from zero"): a nominal value of 17+/-1 includes 17.9, which
would round to 18.
3. assume +/-0.5: This is consistent with rounding, and does not lead to false
precision. As far as I can tell, it doesn't lead to surprises.
We have a bit more freedom with our second use case, comparison during queries,
since uncertainty and rounding are not directly visible to the user. However,
it seems prudent to use the same approach for both cases, to avoid confusion
and inconsistencies.
TASK DETAIL
https://phabricator.wikimedia.org/T105623
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To: daniel
Cc: Jonas, JanZerebecki, harej-NIOSH, Thryduulf, Mike_Peel, Jc3s5h, thiemowmde,
kaldari, daniel, Stryn, Lydia_Pintscher, Liuxinyu970226, Snipre, Event,
Ash_Crow, mgrabovsky, Micru, Denny, He7d3r, Bene, Wikidata-bugs, Ricordisamoa,
Kelson, MSGJ, Wolfvoll, Aklapper, aude
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