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Re: Geiger, not binomial ?

 Correct it's the sample mean.  the mean is found when all have decayed.  However, it's a good estimate, as can be determined by a number of tests.
 

The ref.  used by UCSC Physics is An Intro. to Error Analysis (John R. Taylor)  A thorough use is required by all majors in the Advanced Lab.  They get tested!  I used the ancient bible The Atomic Nucleus  It has a number of counting examples (I think, including how to "deal" with short 1/2 life nuclei.)  (Robley D. Evans)
There are details I skipped, such as bins should be combined so that there are a min of about five in each, etc.

bc

P.s. Do get your students to use (early and often) the Chi Square test.

brian whatcott wrote:

At 11:09 3/23/00 -0600, Glenn Carlson wrote:
>There is every reason to expect your data to fit a binomial
>distribution since it is the correct distribution.  However, as Mr.
>Cleyet correctly points out, the Poisson distribution is more useful
>here because of the huge number of nuclei in your sample (on the order
>of 10^23) and the virtually zero probability that any one nucleus will
>decay during the counting interval.

>//// As you can see
>in the table below, your data with a 0.5 second counting interval fits
>a Poisson distribution very well.  I leave it to you and your students
>to analyze your data with a Gaussian distribution.
>
#counts #times  c*t   c!  P(k;mu(c))  Expected #times =   %diff =
(c)     (t)               (Poisson) P(k;mu(c))*sum(c*t)  |Exp-meas|/Exp*100

0       3321    0     1       0.109586319     3294.712675
/////////
     sum(t) = 30065
     sum(c*t) = 66475

    mean(c) = mu(c) = 2.211042741

>A final note.  Remember to keep in mind that your measured count rate
>is not the same thing as the decay rate of your sample.....
>Glenn A. Carlson, P.E.

Hmmm...it seems we can all learn a little something from this
 puzzle of Ludwik's.
    For example, in Glenn's working above, it would be better to
say that 2.211 is his *estimate* of the mean.

  Using my (incomparable?) least squares method, I see that it is more
likely to be 2.212 +- 0.005 in round numbers - speaking of which,
it is less than pukka to be quoting 10 places of precision anywhere
 in this table: this is statistics, not quantum chromodynamics!  :-)

brian whatcott <inet@intellisys.net>
Altus OK