Variability definition statistics requires us to keep a few very important things in mind. In simple terms, it’s all about how you spread out your numbers (i.e. scores and data) are.
The first concept is range. It’s the highest number that you have minus the lowest value that you have. The second is variance which is Sigma (σ) squared. And last is standard deviation which is the square root of the variance. It’s often denoted by Sigma.
The process includes finding the mean, which is the average of the numbers.
You generally need to find range variance. Once you find the variance, that is the average of the squared differences from the mean, you can find the standard deviation.