GCSE Statistic - Factorials

What is a factorial?

• A factorial shows us how many possibilities there are for a situation
• For n items, there are n! possibilities, therefore n! means we multiply all of the numbers from n, to one. 

For example: 6!

n = 6, so...

6! = 1 x 2 x 3 x 4 x 5 x 6 = 720 different possibilities.

Another example: 4! = 1 x 2 x 3 x 4 = 24 different possibilities.

Example (taken from MyMaths):

6 pupils are lined up for a photo. What is the propability that the tallest pupil is at one end, and the shortest is at the other end?

• First, find out how many possibilities there are for this situation.
• There are 6 students, so we have to work out 6! : 6! = 1 x 2 x 3 x 4 x 5 x 6 =…