Sigma Notation Part 1

Next I want to introduce you to the most common symbol you’re going to see in statistical formulas, sigma notation. Now, this might look intimidating. But it’s actually a really simple symbol. It’s a basic instruction that says add something up. That’s really all it means. Sigma means sum. So just add them up. Add up what? Whatever comes after the sigma. Usually we have parentheses after the sigma. And whatever is in those parentheses, we’re going to add up. It’s a really basic instruction. And it’s going to be really useful. I could put a variable in there. I could put a variable that’s been modified, like I might say square every score and add them up, et cetera.

But we won’t do that just yet. As a basic example, let’s say we’re going with our example of x representing age. So we’ve got these four individuals here with four different ages. So very basically, if I were to say, give me the sigma of x or the sum of the ages, just add them up. 30, 21, 59, and 45 add up to 155. And that’s really all there is to sigma notation. It looks intimidating. It looks really fancy. But it’s a very basic command that says add up whatever comes in those parentheses.