Probability

Probability

Permutations and Combinations

Permutations

• Permutations is an arrangement of members into a sequence or linear order.

•  $_nP_r=\frac{n!}{\left(n-r\right)!}$  

• where n is total number of objects in set

• where r is number of choosing objects in set

Combinations

• Determines the number of possible arrangement in a collection of items

•  $_nC_r=\frac{n!}{r!\left(n-r\right)!}$  

• where n is total number of objects in set

• where r is number of choosing objects in set

What's the difference?

• The order of the elements

For Example...

• In permutations, we care about the order

• AB is not the same as BA

• In combinations, the order doesn't matter

• AB is the same as BA

Multiple Choice

The order does not matter in permutations.

• True

• False

Multiple Choice

Your locker passcode is 5432. Is this a permutation or combination?

• Permutation

• Combination

Multiple Choice

Is choosing 3 desserts from a menu of 10 desserts a permutation or combination?

• Permutation

• Combination