How to calculate mean absolute deviation
- Find the mean x̄.
- Subtract the mean from each value and drop the sign (take the absolute value).
- Add those distances and divide by the number of values.
Example: 2, 4, 6, 8, 10, 12 has mean 7. The distances are 5, 3, 1, 1, 3, 5, which add to 18, so MAD = 18 ÷ 6 = 3.
MAD vs standard deviation
Both measure spread around the mean. MAD uses absolute values, so it is easier to explain (“values are 3 away from the mean on average”). Standard deviation squares the distances first, which gives large deviations more weight; it is always at least as large as the MAD and is the measure used in most further statistics. Middle-school courses (including the US Common Core, grade 6) teach MAD first for exactly this reason.
Frequently asked questions
Is mean absolute deviation the same as median absolute deviation?
No. Mean absolute deviation averages distances from the mean. Median absolute deviation takes the median of distances from the median, and is used in robust statistics. Both are sometimes abbreviated MAD; this calculator gives the mean version taught in school.
Can MAD be zero?
Only if every value is identical, so every distance from the mean is zero.
Does MAD use n or n − 1?
n. There is no sample correction in the usual definition.