As I suspected, there is nearly no correlation between the scores obtained by DCPS teachers on two critical measures.
I know this because someone leaked me a copy of the entire summary spreadsheet, which I will post on the web at Google Docs shortly.
As usual, a scatter plot does an excellent job of showing how ridiculous the entire IMPACT evaluation system is. It doesn’t predict anything to speak of.
Here is the first graph.
Notice that the r^2 value is quite low: 0.1233, or about 12%. Not quite a random distribution, but fairly close. Certainly not something that should be used to decide whether someone gets to keep their job or earn a bonus.
The Aspen Institute study apparently used R rather than r*2; they reported R values of about 0.35, which is about what you get when you take the square root of 0.1233.
Here is the second graph, which plots teachers’ ranks on the classroom observations versus their ranks on the Value Added scores. Do you see any correlation?
Remember, this is the correlation that Jason Kamras said was quite strong.