# Usability Measures in Mobile-Based Augmented Reality Learning Applications: A Systematic Review
## 5 Research Findings on Identified Gaps
### Limited Quality versus Large Sample Convenience (G4)  
One of the well-known facts in usability evaluation is the advantages and disadvantages of performance versus self-reported metrics is either risk of biases or quality of data. In usability, self-reported or subjective measures are merely means opinion-based input given by respondents expressing their experiences. They are also based heavily on subjective judgement of respondentschanneled through instruments such as questionnaires and interviews [135]. As mentioned by [PERSON] in [120], user experience measurements, in general, should essentially be self-reported in order to cover the subjective nature of user experience. However, according to [2; 136] data collected through self-reported techniques can be subjected to social desirability bias and central tendency biases. This can lead self-reported data to be subjected to biases, inconsistencies, and validity. However, the usage of self-reported can reach larger audiences especially through scaled close-ended questionnaires. This might be the reason justifying how evidently through results of data synthesis shows 40 out of 72 scholars used only a questionnaire in tracking usability in MAR, followed by combinations of a questionnaire with other commonly used techniques. According to [101], there is an importance to highlight questionnaires reliability through several correlational approaches. While a total of 60 (57%) authors who used questionnaires as measures, only a handful (12 authors) validated the questionnaires' reliability despite risks of mentioned self-reported biases. Some of the authors who performed reliability measures includes utilization of [PERSON]'s Alpha [12; 14; 32; 40; 42; 49; 57], [PERSON]'s Kappa [15; 24], and [PERSON]'s correlation [15; 22]. Techniques such as performance metrics, which are evidently more reliable than self-reported approach were rarely used under the assumption that these processes are much more technical, time-consuming and tedious. Only a trickle pool of 24 authors (23%) executed performance metrics. A self-reported approach like questionnaire is still used primarily due to the supposition that the processes are swifter and able to reach bigger audiences compared to performance approach. Authors who performed only performance metrics like [28] reached as little as 1 sample, and [36] reachesd 6 samples. Authors like [32; 34] only performed self-reported measures and managed to reach 978 and 318 samples, respectively. Not to mention there are also works who used a questionnaire with smaller samples, as with [62] (11 samples) and [58] (10 samples). Therefore, it is really a matter of opting for quality data within a small pool of respondents using stricter protocols or reaching a bigger audience with convenience by executing simpler procedures despite the risks of questionable and bias data collection. Hence, the identified gaps here are justifications of why self-reported metrics are still widely used despite risks of bias as compared to performance approaches.