Counting Techniques - Stats Module 2

experiment

process by which an observation (or measurement) is obtained

mn rule

If the first stage can be accomplished in m ways and for each of these ways, the second stage can be accomplished in n ways, then there are mn ways to accomplish the experiment.

extended mn rule

n₁n₂n₃…n_k

If the experiment is performed in k stages, with n1 ways to accomplish the first stage…and nk ways to accomplish the kth stage

perumutations of n distinct objects

n!

permutations of n distinct objects taken r at a time

permutations of n repeating objects

n! / n₁!n₂!…n_k!

circular permutations

(n-1)!

combinations

ordering or arrangement of the objects is not important, but only the objects that are chosen. nCr or… (refer to image)