## 2 Background  
### Rapid Guessing in Low-Stakes Testing  
Educational assessment plays a key role in the evaluation of learning outcomes and the determination of students' proficiency levels in diverse contexts [12]. In practice, assessments with important consequences for students (e.g., grades, graduation, certification, and awards) are often considered \"high-stakes\", whereas assessments that do not heavily affect students' grades or other educational outcomes are viewed as \"low-stakes\". However, unlike its name suggests, a low-stakes assessment can also produce important insights for students and teachers, such as more timely information about if and how students are learning, where they may need development to ultimately succeed, and who requires additional support or interventions. Moreover, aggregated scores from low-stakes assessments may yield important guidance at the institutional or governmental level, such as funding allocation, strategic planning for schools, and educational reforms for countries [12]. However, it should be noted that such funding allocations, as well as strategic planning and educational reform, require careful reflection about the long-term outcomes of such incentives for schools, teachers, and students (e.g., [13]).  
Regardless of whether it is a high-stakes or low-stakes assessment, students are expected to put in enough effort while taking an assessment, which in turn becomes a prerequisite for making valid interpretations of assessment scores [14]. However, due to the lack of formal or personal consequences for students, the validity of low-stakes assessments is more likely to be threatened by the presence of aberrant responses and rapid guessing as a result of low test-taking effort [15; 16; 17]. Rapid guessing occurs when students spend a very short amount of time on an item that would not allow them to read and understand the item content properly before making an attempt to provide an answer. The total time spent on each item (i.e., RT value) can be recorded using digital pens in paper-and-pencil assessments (e.g., [11; 18]), while RT information can be automatically collected in computer-based or digital assessments. Using RT information collected from the assessment, responses below a particular RT threshold can be flagged as \"rapid guessing\", while responses above the same threshold are considered \"solution behavior\", yielding a binary index of rapid guessing for each valid response [12].  
Research showed that the presence of rapid guessing behavior may reduce the data quality and contaminate inferences made based on the assessment results, because rapidly guessed items fail to reflect what students know or can do [19; 20; 21]. Ignoring rapid guesses, rather than imperfectly identifying them, is also associated with more disruptive consequences for assessment results [22]. For example, rapid guesses may distort statistical estimates (e.g., the effect of a treatment [23] and achievement gains [24]), undermine classification and prediction models, and bias psychometric properties [25]. They may also generate differential item functioning issues [26] and may trigger problems in test equating [27]. Therefore, researchers and practitioners need to identify and handle rapid guesses to obtain warranted inferences and improve data quality.