Because the order of people does not matter, we can use a permutation to find the answer.
For the first choice there are 15 possible people. For the second one there are 14 possibilities (since one person has already been chosen) and so on.
To get the total number of combinations we do:
[tex]Total=15P4=\frac{15!}{(15-4)!}=\frac{15!}{11!} =15\times14\times14\times13\times 12 = 32760 [/tex]