Dr. Heesun Chang is an assistant professor of Bilingual/ESL Education in the Department of Educational Psychology. With his interdisciplinary expertise in applied linguistics, educational measurement, and statistics, he is interested in analyzing language/discourse patterns and features through corpus and statistical methods to inform language education and assessment. He is also interested in validating/evaluating psychometric properties of assessment/survey instruments. His recent research focuses on analyzing the linguistic features of international teaching assistants (ITAs) to explore, investigate, and evaluate the validity issues in ITA training and assessment.