The mean, as you probably know, is just another name for the average. To calculate the mean of a dataset, all you have to do is sum up all the values and divide it by the number of values that you have.

Let's take this example, which calculates the mean (average) number of children per house in my neighborhood.

Let's say I went door-to-door in my neighborhood and asked everyone, how many children live in their household. (That, by the way, is a good example of discrete numerical data; remember from the previous section?) Let's say I go around and I found out that the first house has no kids in it, and the second house has two children, and the third household has three children, and so on and so forth. I amassed this little dataset of discrete numerical data, and to figure out the mean, all I do is add them all together and divide it by the number of houses that I went to.

Number of children in each house on my street:

0, 2, 3, 2, 1, 0, 0, 2, 0

The mean is (0+2+3+2+1+0+0+2+0)/9 = 1.11

It comes out as 0 plus 2 plus 3 plus all the rest of these numbers divided by the total number of houses that I looked at, which is 9, and the mean number of children per house in my sample is 1.11. So, there you have it, mean.