Can you interpret the sum symbol?

I’ve always find a bit difficult to interpret the sum symbol in Math, but, once you get it, it’s not quite difficult! 😊

Basically, you’re using the Greek letter “sigma” (in capital letters) to express a sum of n values. Take a look at the image below:

In this picture:

“n” represents the last number to be added;
“i” represents the index;
“1” represents the first number to be added and
“X1” represents the X element at the “iest” position.

For example, in the equation below, we want to multiply each value from 0 to 3 by 2 and add their results:

The Mean

We can also represent the mean with the sum symbol, such as this:

In any case,

“n” represents the last number to be added;
“i” represents the index;
“1” represents the first number to be added and
“X1” represents the X element at the “iest” position.

In order to obtain the mean, we then divide the sum by “n” elements!

🐕 In this post, we’ve learned how to interpret the “sum” symbol and to interpret the mean using this symbol.

References:

Field, A., Miles, J., & Field, Z. WHY IS MY EVIL LECTURER FORCING ME TO LEARN STATISTICS?. In: Field, A., Miles, J., & Field, Z. (2012). Discovering statistics using R. SAGE Publications, p. 1-31.

Suggested website:

Khan Academy (In Portuguese)