# Usability Measures in Mobile-Based Augmented Reality Learning Applications: A Systematic Review
## 4 Results and Discussion
### Usability Methods, Techniques, and Instruments (RQ3)
#### 4.4.9 Procedural
** \\ \hline \multirow{8}{*}{**Time-Based Tracking**} & Time-on-task & [20; 23; 29; 36; 39; 45; 46; 47; 48] \\  & Interaction time-on-task & [63] \\  & Time-on-tasks for optimal configuration & [63] \\  & Task completion time & [82] \\
**Time-Based** & Number of time-on-tasks registration & [60] \\
**Tracking** & Time-on-tasks for performance & [38] \\  & Response time & [28; 44] \\  & Time-on-tasks across time & [48] \\  & User decision time & [29] \\  & Time-on-tasks for engagement & [21] \\  & Registering the number of interaction errors & [63] \\  & Number of errors for optimal configuration & [63] \\  & Error rates & [44; 48; 82] \\
**Error Tracking** & Reverse error registration & [36] \\  & Error counts & [39] \\  & Error registration & [28; 29; 46; 47] \\  & Absolute pose error (APE) as evaluation metrics & [28] \\  & Relative pose error (RPE) & [28] \\  & Interview & [12; 16; 23; 51] \\  & Interview (Interviews were transcribed and coded by two independent coders. \\  & The coders assigned a scale value (5=Strongly Agree and 1=Strongly Disagree) \\
**Discussion** & Interview for usability - only interview the teachers & [70] \\
**-Based** & Satisfaction interviews & [80] \\  & 3 rounds of mini-interviews per participant (face-to-face or video) & [50] \\  & Informal interview & [48] \\  & Interview (with teachers, since most students, 9 of them cannot pronounce) & [21] \\  & Group discussion & [51] \\  & Emotion tracking (happy, angry, unmotivated, determined) using video & [21] \\  & recording & [12; 16; 23; 51] \\  & Facial expression (coding through video by 2 independent coders & [42] \\  & Action and impression registration & [23] \\
**Behavior** & Observation on student’s communication and interactivity with peers & [14] \\
**Observation** & Observation on student’s focus on or distraction from the learning material, & [14] \\  & Observation on the way students dealt with the learning object (learning & [14] \\  & &  
In conjunction with RQ3, this study also breaks down the more commonly used usability techniques involving observation, questionnaires, discussion-based (interviews), and procedural/heuristics (cognitive walkthroughs, think aloud, heuristics, expert reviews). Figure 6 shows the seven techniques and percentages of usage across 72 selected studies. Questionnaire (57%) is preferred most by most studies, followed by observation (23%), interviews (11%), expert review (3%), think aloud (3%), heuristic (2%), and cognitive walkthrough (1%). Among the 72 collected articles, 45 utilized only one technique at a time, 18 used a combination of two techniques, 8 utilized a combination of three techniques, and 1 study did not clearly specify specific the technique used. In Table 14, the following abbreviations apply: Questionnaire (Q), interview (Iw), observation (Obs), think aloud (TA), expert review (ER), heuristic (Hc), and cognitive walkthrough (CW). There are a maximum of three usability techniques combination at a time (Table 14). Figure 6 shows the questionnaire to be the largest pool used (57%), which is more than half, combining all the works. Figure 7 shows that although there are many techniques used, some functions are within different combination modes. Table 14 and Figure 7 show that there are 8 scholars who used a combination of three techniques in their research (Figures 8 and 9), followed by a two technique combination (18) (Figures 10 and 11). A majority of 45 scholars used only one technique at a time (Figure 12), while 1 paper did not clearly elaborate on the technique used. Figure 13 shows the frequency of all correlated techniques. For the three technique combination, it can be comprehended that the highest used combination of techniques was that of observation, questionnaire, and interview (4), followed by the combinations of observation, questionnaire, and think aloud (1); observation, think aloud, and interview (1); observation, expert review, and interview (1); and heuristic, questionnaire, and think aloud (1).