Misspellings in responses to listening comprehension questions:Prospects for scoring based on phonetic normalization
Heike da Silva Cardoso, Magdalena Anna Wolska · OPUS (Augsburg University) · 2015
Automated scoring systems which evaluate content require robust ways of dealing with form errors. The work presented in this paper is set in the context of scoring learners’ responses to listening comprehension items included in a placement test of German as a foreign language. Based on a corpus of over 3000 responses to 17 questions, by test takers of different language proficiencies, we perform a quantitative analysis of the diversity in misspellings. We evaluate the performance of an off-the-shelf open source spell-checker on our data showing that around 45% of the reported non-word errors are not correctly accounted for, that is, they are either falsely identified as misspelt or the spell-checker is unable to identify the intended word. We propose to address misspellings in computer-based scoring of constructed response items by means of phonetic normalization. Learner responses transcribed into Soundex codes and into two encodings borrowed from historical linguistics (ASJP and Dolgopolsky’s sound classes) are compared to transcribed reference answers using string distance measures. We show that reliable correlation with teachers’ scores can be obtained, however, similarity thresholds are item-specific.