Training/test data for a decision tree classification algorithm were constructed using the learner corpus of <cite>Kotani et al. (2014)</cite> , which includes learners' judgment of listenability. Listenability was judged by learners of English as a foreign language using scores on a five-point Likert scale (1: easy, 2: somewhat easy, 3: average, 4: somewhat difficult, or 5: difficult).