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Quantifying the statistical error in a counting experiment

  1. Jan 22, 2013 #1
    I need to find the statistical error in a counting experiment. Specifically, a decay can proceed via option A or option B and I need to find the branching ratio BR_a=(N_a)/(N_a+N_b). If I were to do this counting experiment multiple times my results for BR_a would follow the binomial distribution since there are two decay channels.

    How do I quantify the statistical error in my result given that I conduct the experiment only once?
  2. jcsd
  3. Jan 22, 2013 #2


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    Do you have a fixed number of decays ("I take data until I have 100 decays in those two channels")?
    No => you can treat N_a and N_b as the result of independent Poisson processes.
    Yes => the denominator is fixed, and N_a comes from a binomial distribution.
  4. Jan 28, 2013 #3

    Meir Achuz

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    The usual statistical error gives N_A+ - sqrt{N_A}.
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