Mean

Finding an average is often called the "mean." The mean is the most commonly used measure of center.

So let’s find the mean of our dataset. Here again is the dataset of child weights we were using before:

13        36        98        77        42        50       

110      22        49        81        26        38

How do we find the mean? All we do is take the sum of the observations and divide by the count. "Wow," you’re thinking. "I just happen to already have the sum and the count of these numbers!" Good for you. Now you get to use them both.

Just take the sum, which is 642, and divide it by the count, which is 12. The answer is 53.5. So we now know that the average (or mean) weight of the children in our study is 53.5!

So what does this mean? Well, it depends on your study. Maybe you expected that the average weight of the children would be smaller for some reason, so the mean alone is an interesting finding to you. Or maybe you were comparing this group of children with another group of children and found that the other group had an average weight of 84. You would conclude that the other group consisted of much heavier children. Very often, you will find that individual statistics do not mean much on their own, but they take on important meanings when you compare them with others.

Median >>

rev. 15-Jul-2006