The Student Room Group

need some help with averaging results

if I used a ruler with a precision of 0.05cm and I measured the length of something to be 11.10 and 11.45and I calculated that the average of this was 11.28 would i have to round this to 11.30 for example because the precision of the ruler was 0.05? or would I simply leave it to 2dp as 11.28?
Reply 1
you'd need to record it to 0.05cm as well. If you did a calculation you could maybe get away with using 2d.p. I think. (Also, shouldn't a ruler have an uncertainty of 0.1cm? Usual rule is smallest division on measuring device.)
Reply 2
Original post by lerjj
you'd need to record it to 0.05cm as well. If you did a calculation you could maybe get away with using 2d.p. I think. (Also, shouldn't a ruler have an uncertainty of 0.1cm? Usual rule is smallest division on measuring device.)


not sure whether to believe you because i've got people saying that the mean should just be to 2dp and not to 0.05cm from other people.

Not sure whats fact at this point
Reply 3
Original post by lerjj
(Also, shouldn't a ruler have an uncertainty of 0.1cm? Usual rule is smallest division on measuring device.)


Think about it
Reply 4
Original post by Phichi
Think about it


I know why you CAN theoretically measure ±\pm0.05mm with a ruler, it's just that I was under the impression that since measurements which have to pick which mark is closer aren't always great that the usual rule was to give ±\pm0.1mm.

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