## How to find parameters of binomial distribution?

### Clarisha Nijman (view profile)

on 31 Jan 2019
Latest activity Commented on by Star Strider

on 2 Feb 2019

### Star Strider (view profile)

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?

### Star Strider (view profile)

on 31 Jan 2019

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

Star Strider

### Star Strider (view profile)

on 1 Feb 2019
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’.
Clarisha Nijman

### Clarisha Nijman (view profile)

on 2 Feb 2019
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!!!!
Star Strider

### Star Strider (view profile)

on 2 Feb 2019
As always, my pleasure!