# Relative Average Deviation - RAD

I know that RAD is used to expression precision, and I know the formula for it:

Per mil RAD = (abs. deviation)/mean X (1000) for parts per thousand.

Once you find the relative average deviation--this number in ppt--what is the significance of it? What is it supposed to tell you about the data? What does this number represent?? :uhh:

This is probably an elementary topic, but I can't seem to grasp a concrete definition and how it applies to experimental data.

Thanks.