[S] Mixture of 2 binomial distributions

Victor Moreno (V.Moreno@ico.scs.es)
Tue, 9 Jun 1998 12:03:24 +0100


Dear all,

I would like to find maximum likelihood estimates and their
variances for parameters of a mixture of 2 binomial distributions :

p * dbinom(x, m, p1) + (1 - p) * dbinom(x, m, p2)

I think I have managed to get the estimates with nlminb putting
constrains on p, p1, p2 to [0,1], but I don't know how to go on to
get their variances. Also I don't know if this is the best approach.

Could anyone point to a tutorial on this subject or help me?

More details:

I'm using splus for windows 3.3 or 4.0(3)
My real data are: (m=5)
x n
0 344
1 42
2 9
3 3
4 5
5 13

Thank you.
=====================================================
Victor Moreno V.Moreno@ico.scs.es
SERC Tel: 34-93 260 78 12
Institut Catala d'Oncologia Fax: 34-93 260 77 87
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