Answer :
Let the numbers be x1,x2,x3,x4. First calculate the mean of the given numbers. Let the mean be "X". Then calculate mod(X-x1),mod(X-x2),mod(X-x3),mod(X-x4). Add all these modulus terms and divide them by number of terms i.e., 4 in this case. You can take any number of numbers and do this. Hope this helped.
Let the numbers be x1,x2,x3,x4. First calculate the mean of the given numbers. Let the mean be "X". this is the 1st step