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Calculate n in binomial distribution
*To*: mathgroup at smc.vnet.net
*Subject*: [mg101212] Calculate n in binomial distribution
*From*: Peter Breitfeld <phbrf at t-online.de>
*Date*: Fri, 26 Jun 2009 06:55:37 -0400 (EDT)
Suppose I have the following distribution:
cf[n_,p_,k_]=CDF[BinomialDistribution[n,p],k]
Now I want to calculate n so that the biggest n such that e.g.
cf[n,0.2,7]<0.3
I made a ListPlot
ListPlot[Abs[cf[#,0.2,7]-0.3]&/@Range[60]], where I see, that a value of
about n=46 gives an approximation nearest to 0.3
To get this value of n I tried
Minimize[{Abs[cf[n,0.2,7]-0.3],n>7},n,Integers]
Out: {0.699765, {n->11}}
which is obviously wrong.
Why?
Is it, because Abs isn't differentiable at the peak?
I tried other ways too, like Reduce NMinimize, FindMinimum, but no success.
--
_________________________________________________________________
Peter Breitfeld, Bad Saulgau, Germany -- http://www.pBreitfeld.de
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