In the next concepts, we are going to combine what we know about how to calculate the mean with notation. The purpose of this video is not to relearn how to calculate the mean but rather to introduce notation using a measure you already know. Let’s consider the amount of time someone spends on our website in minutes. Imagine we collect the amount of time spent on our site for five individuals. From the last video, we saw that we could label the values in this way, x1 for the first value, x2 for the second value, x3 for the third value and so on. Imagine we want to add the first two numbers together. We could write this in notation as x1 plus x2 which in this example, would be the same as 15 plus 10. If we wanted to add more than just two values, it would be tedious to continue the same process. Imagine if we had 100 values. We would have a, x1 plus x2 plus x3 plus and we’d have to continue this process until x 100. Someone must have come up with a better way to notate this. And it turns out, there is a better way.