What is the difference between k-sample,k-selection, k-permutation and k-combination?

Actually, these all terms are related to the basic concept of choosing some elements from the given collection.

For it, two things are important:

1)      Order of elements .i.e. which one is first, which one is second and so on.

2)      Repetition of elements

So we can get 4 kinds of selections:

1)      The elements have both order and repetition.      ( It is called k-sample )

2)      The elements have only order, but no repetition. ( It is called k-permutation )

3)      The elements have only repetition, but no order. ( It is called k-selection )

4)      The elements have no repetition and no order.    ( It is called k-combination )