The distinction between a combination and a permutation has to do with the sequence or order in which objects appear.A permutation, in contrast, focuses on the arrangement of objects with regard to the order in which they are arranged. Using those letters, we can create two 2-letter permutations - AB and BA.
Translation: n refers to the number of objects from which the combination is formed; and r refers to the number of objects used to form the combination. The combinations were formed from 3 letters (A, B, and C), so n = 3; and each combination consisted of 2 letters, so r = 2.
Note that AB and BA are considered to be one combination, because the order in which objects are selected does not matter.
Instructions: To find the answer to a frequently-asked question, simply click on the question.
If none of the questions addresses your need, refer to Stat Trek's tutorial on the rules of counting or visit the Statistics Glossary. A permutation is an arrangement of all or part of a set of objects, with regard to the order of the arrangement.
In this lesson, we will practice solving various permutation and combination problems using permutation and combination formulas.
We can continue our practice when we take a quiz at the end of the lesson.Each possible arrangement would be an example of a permutation.The complete list of possible permutations would be: AB, AC, BA, BC, CA, and CB.Translation: n refers to the number of objects from which the permutation is formed; and r refers to the number of objects used to form the permutation. The permutations were formed from 3 letters (A, B, and C), so n = 3; and each permutation consisted of 2 letters, so r = 2.For an example that counts permutations, see Sample Problem 1.When statisticians refer to permutations, they use a specific terminology.They describe permutations as n distinct objects taken r at a time.Each possible selection would be an example of a combination.The complete list of possible selections would be: AB, AC, and BC.A combination is a selection of all or part of a set of objects, without regard to the order in which objects are selected.We might ask how many ways we can select 2 letters from that set.