Have a look here: http://web2.0calc.com/questions/what-is-mean-absolute-deviation-of-34-8-36-7-29-3-24-1-17-7-12-9-11-3-10-9-8-9-and-8-9 for an example.
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The steps to find the MAD include:
1. find the mean (average)
2. find the difference between each data value and the mean
3. take the absolute value of each difference
4. find the mean (average) of these differences
Source: http://mathbits.com/MathBits/TISection/Statistics1/MAD.html
Have a look here: http://web2.0calc.com/questions/what-is-mean-absolute-deviation-of-34-8-36-7-29-3-24-1-17-7-12-9-11-3-10-9-8-9-and-8-9 for an example.
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