Combinations and Permutations

Free SOA Exam P (Probability) lesson in General Probability. 17 min read, ~2,608 words.

Fundamental counting principle: multiply the number of choices at each stage; it underlies every permutation and combination formula. Permutations (order matters):. Combinations (order doesn't):; they differ by a factor of. Key question: does rearranging the selected objects create a different outcome? Yes is a permutation, no is a combination. Multinomial...