Kevin Carey wrote for the New York Times about a Tennessee statistician who sought to measure the “value-added” contributions of individual teachers.
Students enroll in a teacher’s classroom. Nine months later, they take a test. How much did the first event, the teaching, cause the second event, the test scores? Students have vastly different abilities and backgrounds. A great teacher could see lower test scores after being assigned unusually hard-to-teach kids. A mediocre teacher could see higher scores after getting a class of geniuses.
Thirty-five years ago, a statistician, William S. Sanders, offered an answer to that puzzle. It relied, unexpectedly, on statistical methods that were developed to understand animal breeding patterns.