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Implied precision

  1. Oct 12, 2016 #1
    • Member advised to always provide an attempt at solution for homework questions
    1. The problem statement, all variables and given/known data
    Some sources say the implied precision of a measurement is half of the least significant figure, while others say the implied precision is "1" in the place of the least significant figure.

    For example, a length is measured as 3.28 m. According to some sources, the implied precision is 0.005 m, while according to other sources, the implied precision is 0.01 m. Which is correct and why?

    2. Relevant equations


    3. The attempt at a solution
     
  2. jcsd
  3. Oct 12, 2016 #2

    phinds

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    What do you think and why?
     
  4. Oct 13, 2016 #3
    I think it depends on the measuring instrument. If it's analog, half of the smallest division; if it's digital, the smallest division.

    So in this case, if it's a measured length, I'd assume the instrument is analog and the implied precision would be +/- 0.005 m.

    Does this sound right?
     
  5. Oct 13, 2016 #4

    phinds

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    Doesn't sound right to me. The imprecision does not seem to me to be related in any way to how the measurement is PRESENTED. Things like temperature, pressure, and so forth are analog in nature and are of necessity measured as analog things. How the result is then presented has nothing to do with the imprecision in the fundamental measurement.

    Yes, you can have instruments that directly produce digital results but that does not change the fact that they are measuring analog characteristics and the question is, what is the imprecision of when they change from one measurement to their next digital increment. THAT is still analog.
     
  6. Oct 14, 2016 #5
    So I should always assume half of the smallest division?
     
  7. Oct 15, 2016 #6

    phinds

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    That's what I always do.
     
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