## 2 Background and Related Work
### Related Work
#### 2.2.1 Usability and User Experience  
Educational chatbot evaluation must consider both usability metrics (user satisfaction, efficiency, and effectiveness in specific environments) [45] and broader user experience (UX) factors, including emotional responses and learning engagement [46].  
A comprehensive assessment of over 700 publications, drawing from 28 original studies, revealed experimental approaches for evaluating chatbot usability through a systematic mapping study [47]. The authors deduced that usability in chatbots is often characterized by effectiveness, efficiency, and satisfaction. Therefore, while usability evaluations for chatbots are increasing in volume, experimental methodologies often lack standardization and transparency. Few studies provide raw data or include experimental replications, limiting replicability and comparative value across studies.  
The System Usability Scale (SUS), originally developed by [PERSON] [48], and the Usability Metric for User Experience (UMUX)-LITE [49], an adaptation of the UMUX, are both streamlined tools for assessing usability, although each serves slightly different purposes. The SUS, a widely adopted 10-item tool, provides a comprehensive and efficient measure of the overall UX with a system.  
In contrast, the UMUX-LITE, with just two items focused on effectiveness and ease of use/efficiency, offers a rapid yet reliable snapshot of user experience, ideal when time constraints make the full SUS or other more comprehensive measures impractical. Together, the SUS and UMUX-LITE capture the core usability dimensions, enabling flexible usability assessments across various contexts. Research has shown strong correlations between UMUX-LITE and SUS scores, indicating that, despite its brevity, the UMUX-LITE provides comparable insights into perceived usability, often sharing around 70-80% of the variance with the SUS and other usability metrics [50].  
However, the design and testing of a usability scale should be tailored to evaluate chatbot interactions [51]. This study proposes the Bot Usability Scale (BUS-15), focusing on conversational attributes such as efficiency, functionality, accessibility, and engagement aspects, which are often not covered by traditional usability tools such as the UMUX-LITE. Therefore, the BUS-15 assesses interaction quality with conversational agents by capturing usability and engagement attributes relevant to the chatbot. Thus, this metric could be refined for a composite metric approach, enhancing the precision of capturing UX across educational chatbot interaction modes. While existing usability scales such as the SUS and UMUX-LITE are valuable for general usability assessment, specialized tools like the BUS-15 address the unique conversational attributes of chatbots. This study extends these approaches by integrating usability (CUQ), engagement (UES-SF), and task effectiveness into a composite metric for holistic assessment, tailored to Arabic educational chatbots.  
Consequently, based on our investigation and a recent systematic mapping study [52], despite a growing interest in chatbot usability, recent systematic reviews reveal significant gaps in standardization and a lack of consensus on best practices. This highlights the need for a comprehensive and replicable evaluation framework that integrates key UX dimensions, addressing the limitations of existing approaches.