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Homework Help: Checking my probability

  1. Jan 16, 2006 #1


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    I was hoping that somebody would check my work. Any input is appreciated.
    A decay rate of a radioactive sample is being measured using a Geiger counter. During a 10 second measurement 100 decays are registered.
    what is the error associated with the result?
    [tex]\sigma_{y} = \frac{\sigma}{\sqrt{N}}[/tex]
    My work:
    [tex]\sigma^2 = np = (100)(1/10) = 10[/tex]
    so [tex]\sigma = \sqrt{10}[/tex]
    putting this into the previous equation where I make N=100 I get an error around 0.316. Did I do that right?
  2. jcsd
  3. Jan 17, 2006 #2
    If you are loking for the standard deviation for the count rate, then your correct equation should be sqrt(n)/t where n is your count and t is the count time. If you are looking for the standard deviation for the count, then it's just sqrt (n).
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