Can someone show me how to do mean absolute deviation
what is the means-to-mad ratio of the two data sets, expressed as a decimal?
data set mean mean absolute deviation (mad)
1 10.7 2.4
2 13.7 2.5

To find the mean of a set, add up all of the numbers and divide by how many numbers you have. For the first set:

For the second set:


To find the mean absolute deviation, (MAD) find the mean of the distances of each number from the mean.
For the first set: 

For the second set:

Note that when you only have two data points the mean is directly between them, which is why the distances are the same.

The means-to-MAD ratio is simply that, divide one by the other and that's it.
For the first set:

For the second set: