In: Statistics and Probability
I’m a little confused as to when to calculate the possibility using factorial, raise to the nth power and multiplication.
For example: roll a pair of 6-sided dice and there will be 36 outcomes. In this case I assume it’s 6*6 = 36
However, when should I use 6! or 6^6?
Thank you!
Consider the same example of rolling a die. If you want to see all possible number of outcomes on n rolls, you use, 6n
That is, if rolled 2 times, number of outcomes = 62
If rolled 5 times, number of outcomes = 66
If you want to count the number of cases in which no letters can be repeated, number of possible outcomes = 6!
So, the basic difference is that when repetition is allowed, you use nth power and when repetition is not allowed, you use factorial.
A better example of a situation where you chose factorial is given below.
You have a list of 5 songs. You are interested in number of arrangements possible. The number of ways to arrange 5 songs = 5!
Here, we used factorial because songs are not repeated.
If A,B,C,D and E are the songs, then B,C,E,A,D is an arrangement of the song, but not B,C,B,B,E. In case of rolling a die, 3,2,5,1,6,4 and 3,2,5,2,5,5 is also a possible outcome and hence, we use nth power in that case.