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Please help me.....

  • To: mathgroup at smc.vnet.net
  • Subject: [mg91072] Please help me.....
  • From: "Dewi Anggraini" <dewi_anggraini at student.rmit.edu.au>
  • Date: Tue, 5 Aug 2008 04:03:10 -0400 (EDT)

Hi all

I'm an international studentat RMIT University Melbourne. Currently, I'm 
doing my master degree in Statistics and Operations Research. This
following 6 months will be my last semester to finish my master degree.
Therefore, I have been doing minor thesis about "estimating unknown
parameter of Burr distribution" by using Mathematica.

I was wondering if this forum could assist me to detect where I got wrong
with my program since it works for Burr distribution in some data but not
with my data. Additionally, this program (I attached my program along with
my data) also works for non-normal distribution, such as Gamma and Weibull
since my data are non-normally distributed and they are closely to gamma
and weibull distribution.

The data are treatment time of cervical cancer patients in a hospital.
Frequently, they come to the hospital in the late satge of cancer, thus
the minimum time for the treatment is 2 days and the maximum treatment on
the data is 21 days.

The following is my program to run MLE of Burr distribution. However,
it comes up with "comment" results in finding the coefficient of unknown
parameters when I run it.


n = 69;
x2 = {5, 6, 5.5, 5, 8.4, 4.5, 4, 6, 7, 6, 7, 8, 5.4, 5, 4, 3.5, 4.5,
       6.5, 5, 3.5, 5.7, 5.8, 5, 4.8, 4.5, 5.8, 3.2, 6, 4, 6, 7,
   6.5,
       10.7, 7, 4.7, 7, 8.3, 10, 6.5, 4.9, 3.4, 9, 6, 3.1, 5, 4.8, 4,
   6,
       6, 5.6, 4.2, 4.3, 4.5, 8.4, 8.6, 5.8, 6.8, 4.8, 3.4, 8, 8,
   8.3, 8,
       4.5, 6, 4.5, 7, 7, 8};
BurrDistribution[x2_, c_,
  k_] := (c*k)*(x2^(c - 1)/(1 + x2^c)^(k + 1))
pdf = BurrDistribution[x2, c, k]
logl = Plus @@ Log[pdf]
maxlogl = FindMinimum[-logl, {c, 1}, {k, 2}]
mle = maxlogl[[2]]



Please assist me in finding the problem I face now. This is very important
for my thesis.

I look forward for any comments and advices, thank you.

Regards,
Dewi


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