To calculate standard deviation, we must do the following:
1. Find the mean of our set of data...
2. Take the difference of each piece of data and the mean...
3. Square each of them...
4. Sum the squares in the previous step...
5. Divide by the number of pieces of data...
6. This gives us the variance. To find the Standard Deviation, take the square root.
Marcos watched a few examples of this, and then worked through a few exercises on his own. He did a good job with it!