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Timeline for The uncertainty of a metre ruler?

Current License: CC BY-SA 3.0

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Dec 30, 2015 at 22:18 comment added Carl Witthoft Fair enough!ONEONEONE (needed more chars to be able to post)
Dec 30, 2015 at 21:41 comment added Floris @CarlWitthoft I understand that. My point was that a ruler with 0.1 mm graduations is likely to be no more accurate than 0.1 mm - and possibly less. Which is why I am advocating against trying to estimate subdivisions.
Dec 30, 2015 at 21:02 comment added Carl Witthoft Careful: you're mixing accuracy and precision there. A ruler which has 0.1mm gradations will give you an answer with precision of 0.05mm but the entire ruler might only be accurate to 20% if it was built badly.
Dec 30, 2015 at 19:06 comment added Floris @msh210 while it is possible to estimate subdivisions, you have to be careful about interpretation of the error: was the ruler intended to be that accurate? In other words is the scale sufficiently linear to allow that interpolation? Usually the answer is "no". 1 mm on 1 m is 0.1% which is actually rather good...
Dec 30, 2015 at 18:49 comment added msh210 +1. Re "if… quoting the number you read… (assuming it is marked in mm) and you thought the nearest value was 345 mm, then… ask… could it have been 346? If your measurement was 'almost half way' between two values the answer is clearly 'yes', and you can see you would be wrong to say +- 0.5 mm": Right, but that's only because you're choosing imprecision. If instead you say exactly what you think you see (e.g. "345.4 mm" even though the lines are 1 mm apart), you won't be off by more than 0.5 mm (for this reason). But you need to drop a digit after e.g. multiplying that measurement.
Dec 30, 2015 at 15:50 history edited Floris CC BY-SA 3.0
added 154 characters in body and picture
Dec 30, 2015 at 13:39 history answered Floris CC BY-SA 3.0