How can I determine the expected sum of randomly chosen numbers from vector? (combinatorics)

Hello there,

I would like to solve the following problem with Matlab.

If you choose two numbers out of this vector [-1 -1 -1 1], what is their sum, on average?

With nchoosek(4,2) I can determine that there are 6 combinations, but how can I iterate through these combinations to determine each of the 6 sums?

Thanks,

Tobias

Answer 1

[Joost]

The nchoosek function can give you all combinations of 2 elements from the vector.

Instead of nchoosek(4, 2), use nchoosek([-1 -1, -1, 1], 2)

I am not sure how it deals with replicas.