What is a Mean Absolute Deviation?

The past couple of weeks have been filled with students working on projects ranging from measuring their height and shoe size for scatter plots, to students practicing standing long jumps for work in the area of measures of central tendencies. The 7th grade did a great job of working with the averages of smaller groups and comparing them to groups from a different class period.

This had me thinking of teacher evaluations and how our numbers might "stack up" against someone else's scores. Generally, we would be given the average of the scores generated from both announced and unannounced observations. The average of those visits would be put into a formula to determine my "effectiveness" as a teacher.

The above mentioned 7th graders also had to determine the Mean Absolute Deviation (MAD) from a set of numbers. This is where we determine how far the individual scores are from the average of the group. The smaller the MAD is, the less variability is in the set of numbers. The higher the MAD, the more variability there would be. I started thinking if this should be added to our teacher observations as well.

For instance, a teacher with a low MAD would show much more consistency than someone who did not. The teacher with a higher MAD may have spent more time planning for the announced observations than when someone just "popped in". In my opinion, this lack of consistency should not be taken lightly.

A teacher that is much more consistent, meaning a low MAD, would show much more consistency in their daily planning. In my opinion, this teacher would not just "put on a show" when it is announced observation time. I know this takes a great level of confidence, but I think this should somehow be added to our observation "score".

I apologize if this just seems like I am rambling, but I am trying to show my students how I would connect what we are working on in the classroom to a real-life situation.

Any thoughts on the addition of the Mean Absolute Deviation to our teacher observations?
Please share....