Dr. J's Guide to Permutations

Permutations (without replacement) are an ordered set of k elements taken from a set of n elements where elements cannot be repeated. In constructing this set, we have n choices for the first element, (n-1) choices for the second element, and so on until we have (n-k+1) choices for the kth element. Thus the formula for the number of permutations without replacement is n factorial divided by (n-k) factorial. This formula is applied to cross-over clinical trials to determine the number of possible treatment plans and to shuffling a deck of cards to determine how many different arrangements of those cards there are.

• Slides: http://jaradniemi.com/video/dr-js-guide-to-permutations-without-replacement/

00:39 - Fundamental Rule of Counting 02:49 - Intuition behind the permutation formula 05:20 - Cross-over clinical trial 07:19 - Shuffling a deck of cards 08:53 - Summary ... https://www.youtube.com/watch?v=9M9i6kFzv3s