There are really 3 different parts of this topic:
1: Calculating the mean (average)
So, let's say we have this set of numbers:
3, 7, 4, 8
We want to know what the average in this group is.
First we add all our numbers together:
3 + 4 + 7 + 8 = 22
Now we divide 22 by the NUMBER of NUMBERS we had in the first place: 4. (We started off with 4 numbers).
22/4 = 5.5
For this, it doesn't matter if your answer isn't a whole number.
2) Calculating the median
For this, we want the middle number in our set, regardless of what the other numbers are. In our previous example, (3, 7, 4, 8,) first we have to put the numbers in order:
3, 4, 7, 8
And now we can see that, actually, there is no middle number. So what do we do? Well, we take the two numbers closest to the middle (4 and 7) and find the number exactly in between.
7 - 4 = 3
3/2 = 1.5
4 + 1.5 = 5.5
In this case, it happens that the median is the same as the mean. However, in some cases they can be very different!
3) Calculating the mode
The mode is the MOST COMMON number among all of them. In our last example, there is no mode, as all the numbers appear only once. Let's have a new one:
1, 2, 3, 2, 4, 3, 1, 2, 2
Ok, now we count up all the numbers, and find there are:
Two 1s
Four 2s
Two 3s
One 4
As we can see, 2 is the most common number, so it is the mode.
Here is a quick quiz to test yourself on all three methods:
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