The Correlation Between ‘Value-Added’ Scores and Observation Scores in DCPS under IMPACT is, in fact, Exceedingly Weak

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.

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5 CommentsLeave a comment

  1. I hate you.


    • Hmm. Is this really Jason Kamras? I doubt it. And I don’t really know you personally, but if the writer (you) are really JK himself, you have had a profoundly negative impact on education all across the US. And you are probably quite proud of it, too.


  2. I thought that you DCPS got rid of Ms. Rhee. Your data seem to suggest that she is still running things. Keep us posted.


    • Her faithful henchperson and enablers are running things in dc
      However Rhee is now on the national stagecausi g trouble for teachers, students and parents.


  3. Yet when Jason Kamras was named Teacher of the Year, he didn’t believe in this shit.
    Power tends to corrupt, and absolute power corrupts absolutely.


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