# Usability Measures in Mobile-Based Augmented Reality Learning Applications: A Systematic Review
## 4 Results and Discussion
### Correlational Usability Mapping (RQ4)  
Section 4.2, Section 4.3, Section 4.4 have, respectively, presented the common domains, research types, contributions, metrics, methods, techniques, and instruments used in MAR-based usability studies. In order to answer the fourth research question, two-dimensional and three-dimensional mappings have been employed to demonstrate co-relational factors of these collected data attributes. First, three main components--namely research types and contribution types--were mapped against the general usability metrics of performance, self-reported or combination of the two. It can be seen in Figure 14 that most studies engage in exploratory studies use self-reported metrics (32), followed by comparative studies that also utilize mostly self-reported metrics (24). The least used combination of research types and metrics are exploratory with performance (1), empirical with performance (1), and comparative with performance (1). On the other hand, most studies that contributed to the research of tools employ mostly self-reported metrics (27), followed by a hybrid of performance and self-reported metrics (13). The least used combination of contribution types and metrics are tool and performance (1), technique and performance (1), and model and hybrid metrics (1). Figure 12: Papers with one main technique. Figure 13: Frequency of correlated techniques. The second correlation relates to a three-dimensional mapping of the mentioned metrics (performance (white), self-reported (grey) and hybrid metrics (dark grey)), research types, and contributions types. The mapping in Figure 15 shows that most studies have conducted exploratory research used self-reported metrics in the contributions of producing the MAR tool (18), followed by 12 papers that conducted comparative research using self-reported metrics in producing the MAR tool as their major contribution. Figure 16, on the other hand, presents a two-dimensional mapping of research types with seven commonly used usability techniques, followed by contribution types with the seven usability techniques. It can be seen in Figure 16 that the largest population belongs to groups of scholars who carried out exploratory research with questionnaire (36), followed by comparative research with questionnaire (34). As for techniques and tools combination, the largest pools incorporate research that combines questionnaire with tool contribution (33), followed by the combination of observation and tool contribution (14). Figure 17 shows a two-dimensional mapping on the correlational relationships of research types with types of evaluation and contribution type with types of evaluation. It can be interpreted from  
Figure 14: Two-dimensional mapping of research types, contribution types, and metrics. Figure 15: Three-dimensional mapping of research types, metrics, and contribution types. Figure 17 that most researchers who conduct exploratory research evaluate respondents using the between-subjects technique (32), followed by comparative research, which also uses the between-subject evaluation technique (20). On the other hand, the largest pool of researchers who produce tool-related contribution also utilizes the between-subjects method (30), followed by tool-related contribution with within-subject (7), and the model-related contribution with between-subjects testing (7). In can be derived from the analysis that the largest pool of researchers uses questionnaires when measuring through between-subjects testing (41), followed by a questionnaire with within-subject testing (15). Subsequently, most scholars who use between-subjects testing performed self-reported metrics (36), followed by self-reported metrics with within-subject testing (11), and hybrid metrics with between-subjects testing (11). Referring to Figure 18, a three-dimensional mapping has been constructed to better understand the three-way correlation between common usability techniques, evaluation types and used metrics.