# AdaBoost: Why does test error decrease even after training error hits zero?

After applying AdaBoost to the Sonar data, I obtain something like this.

I dont understand that phenomenon, can anyone enlighten me?

• It appears to be related to how confident AdaBoost is in correctly classifying the observations. See Schapiro and Freund's book, p16 has some introductory remarks that point to later chapters. – Christoph Hanck Sep 4 '15 at 15:13