Range: It’s the difference between the highest (largest) value (H) - the lowest (smallest) value (L) pieces of data.
so range = H(highest value) -L(lowest value)
-----> some people also look at this as range= max(x) - min(x)
Variance: Is a sample measure of the spread of data about the mean.
Mean absolute deviation: tells us the average distance that a piece of data is from the mean.
What are the formula for these?
To find the formulas for these parts of standard deviation look through this great pdf, find the glossary section on the far right hand side and look
under measures of dispersion.
http://www.statistics.com/resources/statsymbols.pdf
This video describes what the variance is and shows us examples of how to calculate it. (It does briefly go into standard deviation)
Source: Khan Academy
