The formula for standard deviation isn't a hard formula, but it might be the hardest one that you have tried to learn so far.
This tutorial is designed to aid you in the learning of this formula in a way that will also teach you its meaning.
The complication of the formula itself is compounded by the fact that there are two different formulas.
The Population Standard Deviation is given by the formula:
The Sample Standard Deviation is given by the formula:
The only difference between these two formulas is that we divide by N in the population standard deviation and by n-1 in the sample standard deviation.
We will learn both of these, but we will first learn the population standard deviation because it "makes more sense."