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I Uncertainty Calculations

  1. Mar 1, 2016 #1
    Hi,

    I'm doing a lab report and for every number we need to calculate the uncertainty. I tried to calculate by using the SQRT of the number but i didn't get the same answer as my partner had?
    could you help me!!

    These are the numbers and the uncertainty of my partner which i could not figure out how it was done!

    upload_2016-3-1_14-1-27.png
     
  2. jcsd
  3. Mar 1, 2016 #2

    RUber

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    It appears the uncertainty was calculated as
    ##\sqrt{2CPM}##.
     
  4. Mar 1, 2016 #3
    Thanks RUber for the fast reply.

    Are there any other way to calculate the uncertainty ?
    And how can i know i'm using that right way?
     
  5. Mar 1, 2016 #4

    RUber

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    Normally, the uncertainty comes from your measurement tool, or from the process itself.
    Without more information about the expected relationships between your data, I am not sure why you would choose one method over another for uncertainty estimation.

    In this document (http://instructor.physics.lsa.umich.edu/int-labs/Statistics.pdf) there is a reference to the "square root rule," which generally says if you know nothing else about a number (large integer), the standard deviation is the square root of the number.

    Assuming CPM is a measure of some C per minute, then it might make sense that your count for 2 minutes was 2*CPM.
    Then the uncertainty in that measurement would be (using square root rule) ##\sqrt{2 CPM}##.
     
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