Self-selection bias in the sensitive topic of teacher grading: the role of subject and school context

Self-selection bias in voluntary questionnaire surveys poses a threat to the validity of research findings, particularly when studies address sensitive topics. This paper reports on an unexpected case of self-selection bias encountered in research on teachers’ grading beliefs and practices in Austria. Originally designed to examine the relationship between teachers’ grading beliefs and their actual grading behavior, the study revealed systematic differences between respondents and nonrespondents