> On 19 Sep 2015, at 19:16, Daniel Kinzler <[email protected]> wrote: > > Am 19.09.2015 um 10:27 schrieb Egon Willighagen: >> >> >> On Tue, Sep 15, 2015 at 10:12 PM, Michael Peel <[email protected] >> <mailto:[email protected]>> wrote: >> >> It seems to assume a default uncertainty on values, though: I just added >> the >> elevation above sea level to: >> https://www.wikidata.org/wiki/Q1513315 >> just specifying the central value, and it assumes that this value is +- >> 0.1 >> km - which isn't a good assumption to make... >> >> >> Did you mean to write 2.80 km about sea level? Then the error would be 0.01 >> km >> .... I am guessing the uncertainty follows the scientific notation of the >> number... 2.8 has the numeric uncertainty of (about) +/- 0.1... >> >> That sounds like a reasonable approach to me... > > Yes, the uncertainty follows the scientific convention about significant > digits.
Taking that approach is a *really* bad idea. You can't just assume/make up uncertainties! As an example, say you have a length of 100m. Which significant digit do you assume is correct? Is this +- 100m, 10m or 1m? What if it's referring to the length of a 100m run, where the accuracy could be much higher than the significant digit given, e.g. 100m +- 1cm? Or what if it's the size of a crater on a distant planet, where it might be 100m+-50m? Or if the actual value is 100m +- 3m, but we say that it's +- 1m (which I see is the default in this case), which might be believable to readers but very misleading in reality? > We are currently thinking about adjusting this a bit, see > https://phabricator.wikimedia.org/T105623 As thiemowmde says there: "The fact that the parser "guesses" a precision based on basically zero information always was and still is wrong. It must default to ±0. Everything else is misleading and a source of significant confusion and actual errors." ... although perhaps a better approach if possible might be to default to -1, or something else indicating the absence of data. Thanks, Mike _______________________________________________ Wikidata mailing list [email protected] https://lists.wikimedia.org/mailman/listinfo/wikidata
