How to find the mean absolute deviation

Add all the numbers together to get the sum.
Divide the sum by the number of numbers to get the mean.
so you have
1,2,3,4, that is 10. divide ten by four. because there are 4 numbers.
you get 2.5. Take each number and subtract 2.5. Discard all the negatives from the pile. So in essence you are taking the above example and subtracting 2.5 from 3 and 4 because the other two are going to be negative. so the answer is 3 - 2.5 and 4 - 2.5 which is 2. then take that 2 and divide by the number of items that you subtracted from which is 2. 2/2 is 1. one is the mean standard deviation.