# Implementing and Evaluating a Font Recommendation System Through Emotion-Based Content-Font Mapping
## 5 Usability Evaluation of the Font Auto-Recommendation System
### Usability Evaluation  
To evaluate the usability of the content emotion-based font recommendation system, three usability metrics were employed: the appropriateness of the recommended fonts concerning how well they matched the content, satisfaction with the recommendations provided by the system, and the efficiency of the content-based font recommendation system. The evaluation categorized the recommended fonts into four groups based on their ranking. Group 1 included fonts ranked from 1 st to 6 th; Group 2 included fonts ranked from 7 th to 12 th; Group 3 included fonts ranked from 13 th to 19 th; and Group 4 included fonts ranked from 20 th to 26 th. Figure 5: Examples of recommended fonts derived from the analysis of blog content. (**a**) In the case of (**a**), it is a blog post containing content related to sadness, and below the red arrow are the font recommendations based on blog post content and image analysis, respectively. The font recommendation results can be applied to the blog’s title, and user selection is possible. (**b**) Similarly, in the case of (**b**), it represents a blog post with challenging and angry content, along with the font recommendation results. Participants were presented with various facial expressions and text content to determine the appropriateness of the system's results. They were asked to select the most appropriate and least appropriate recommendation groups for each piece of content, providing an evaluation of the appropriateness of the system's results. Additionally, participants were asked to rate their satisfaction with the results for each recommendation group on a 7-point Likert scale. The Likert scale is commonly employed in usability evaluations for its simplicity, clarity, and effectiveness in quantifying and comparing user experiences across various aspects such as interface design, product features, or service quality. Its concise numeric measurements provide an integrated assessment, facilitating statistical analysis and trend observation. The scale's universality and ease of understanding make it applicable to diverse user groups, enhancing user feedback accessibility. Moreover, Likert scale scores exhibit consistency, allowing for reliable usability tracking and comparisons over time or among different user cohorts. Overall, the Likert scale serves as a versatile and objective tool in usability evaluations, promoting efficiency in data collection and analysis. Furthermore, users were invited to directly experience the font recommendation system and compare it with the existing font recommendation system developed in previous research [13] to assess the efficiency of the system when receiving font recommendations. The evaluation was also conducted using a 7-point Likert scale. Table 4 provides details about the evaluation criteria and measurement methods. The reason for utilizing the three metrics--Appropriateness; Satisfaction; and Efficiency--in the usability evaluation is as follows: First, each metric comprehensively assesses different aspects of the system. \"Appropriateness\" gauges the degree to which the system aligns with its purpose; \"Satisfaction\" measures the user's contentment; and \"Efficiency\" evaluates how efficiently tasks are performed. These metrics align with the core principles of user-centered design. \"Appropriateness\" ensures that the system meets user requirements and accomplishes user-centered goals. \"Satisfaction\" indicates how positively users experience the system, and \"Efficiency\" emphasizes reducing user effort and promoting efficient task performance, aligning with user-centered system design principles. These metrics are widely used in usability evaluations, addressing key aspects of the user experience. Appropriateness, Satisfaction, and Efficiency collectively reflect user needs, impacting the success of the system and user satisfaction. Moreover, these evaluation metrics are applicable to various types of systems and user groups and are widely recognized and utilized in usability evaluations [23; 24; 25; 26; 27].