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Errors in measurements

  1. Oct 26, 2009 #1
    This has been very comfusing. Is the error in taking a reading the smallest or half the smallest division? Say a standard 30cm ruler, you can judge to nearest 0.5mm but since you take 2 readings you need to double the error. But then in titrations using a lab burette you count the titre as half the smallest division? I am very confused here as I cannot decide what to put when a question in an exam asks for the error in the reading.
     
  2. jcsd
  3. Oct 29, 2009 #2
    For measurements of this type, where all the random uncertainties (not errors!!) are equal and there are no systemantic uncertainties:
    For n measurements:
    Add all the measurements and divide by n to get average (don't use rms here).
    Divide the uncertainty of one measurement by sqrt(n) to get the uncertainty of the average.
    Bob S
     
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