In international large-scale assessments, students may not be compelled to answer every test item: a student can decide to skip a seemingly difficult item or may drop out before the end of the test is reached. The way these missing responses are treated will affect the estimation of the item difficulty and student ability, and ultimately affect…

Questionnaire scales that are mixed-worded, i.e. include both positively and negatively worded items, often suffer from issues like low reliability and more complex latent structures than intended. Part of the problem might be that some responders fail to respond consistently to the mixed-worded items. We investigated the prevalence and impact of…