Mean is one of the 3 measures of central tendencies in math... these three are mean, median , and mode.... Mean is the one that takes the average of all the numbers in the list. To find the mean, you must add all of the numbers together, and then divide by the amount of numbers that you added... Keep in mind that the mean can be a decimal and is the only one of the three that doesn't have to be a number in the original list. Here is an example on how to find mean:

example list of numbers : 21, 24, 35, 35, 52, 23, 21, 21, 20, and 32

- first add them all together

21+ 24 +35 + 35 + 52 + 23 + 21 + 21 + 20 + 32 = 284

- then count how many numbers you added

there were 10 numbers

- then divide the sum you found by the amount of numbers you had

284 / 10 = 28.4

Therefore the mean (or average) from that example is 28.4

Basically, the "!" means an operation called factorial. This is an operation that takes an integer, n say, and returns the product of the integer and all the integers smaller than that integer. In other words we have:

n! = n*(n-1)*(n-2)*..*2*1.

By convention we understand 0! = 1.

The factorial emerges naturally in the mathematics of combinatorics and discrete probability.

For example, if you have the 10 numbers, {0,1,2,3,.,9}, you might ask the question: How many ways can these numbers be put in order without repeating any of them.

Clearly you will have 10 choices for the first number, 9 for the second number, and so on.

So there will be 10! different ways of ordering these 10 numbers without replacement.

The (!) in math is called a Factorial. Factorial means that you take a number and multiply it by every number lower than it but Not Zero. So... if you have something like 6! the Six Factorial is:

6 x 5 x 4 x 3 x 2 x 1... Factorial goes until it reaches the number 1. However sometimes when calculating the factorial people exclude the 1 since any number times (x) 1 IS that number! so going back to the 6 Factorial...

6! = 720

(6 x 5) x (4 x 3) x (2 x 1) = 720

30 x 12 x 2 = 720

Im sorry, i totally read that wrong... ! is the symbol for factorial which means you multiply all the integers below that number by that number until you get to 1... For instance, 3! means 3*2*1 = 6 or 10! is 10*9*8*7*6*5*4*3*2*1 = 3,628,800... sorry about that :)

...! is the symbol for factorial.

n! is defined as n(n-1)(n-2)(n-3)....3.2.1

so 3! is 3 x 2 = 6

4! is 4 x 3 x 2 = 24

5! is 5 x 4 x 3 x 2 x 1 = 120