Combinations and Permutations

• When the order doesn't matter, it is a Combination.

• When the order does matter it is a Permutation.

Independent Event / Dependent Event

Two events are independent if the occurrence of one event does not affect the probability of the other event occurring.

Two events are dependent if the occurrence of one event does affect the probability of the other event occurring.

Consider choosing two objects randomly, one after the other, from a group of objects.

Let's say you replace the first object before making your second choice. Then the two choices are independent events.

If you do not replace the first object, then the two choices are dependent events.