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How to find parameters of binomial distribution?

Asked by Clarisha Nijman on 31 Jan 2019
Latest activity Commented on by Star Strider
on 2 Feb 2019
Dear all,
What code can I use in matlab to find the parameters of a binomial distribution? This question is very big. So I am restricting it to a specific situation.
X is binomiallly distributed with parameter n and fraction p. The parameter p is unknown.
What function in matlab can help me to find that parameter if for example it is known that X=randi(10,20,1); P(X<=4)=0.3?
Thank you in advance.

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1 Answer

Answer by Star Strider
on 31 Jan 2019
 Accepted Answer

If you have the Statsitics and Machine Learning Toolbox, see if the binofit (link) function will do what you want.

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For that problem, this appears to be the correct approach:
X=randi(10,20,1);
Px4 = nnz(X <= 4)/numel(X); % Single Probability
[P,Pci] = binofit(Px4, numel(X)) % Binomial Probability Of A ‘Px4’ Fraction Of ‘X’ Being <= 4, Those Being Defined As A ‘Success’
If you run this several times, you will get different results for each iteration, depending on the elements of ‘X’. and therefore the value of ‘Px4’.
That is it!!!!!!
the problem was the interpretation of the first parameter of the binofit function.
But now I understand, x is not the number of the succeses, but the probability of success in a given binomial trial based on the ACTUAL number of successes,
Once more thanks a lot!!!!
As always, my pleasure!

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