## 3 Results and Discussion
### Answering RQ3 to RQ5
\begin{table}
\begin{tabular}{c c c c} \hline \hline
**Year** & **Ref.** & **Programming Language** & **Functionalities Library/SDK** & **3D Content Creation** \\ \hline
2019 & [197] & N/A & Mathlab & N/A \\ \hline
2019 & [204] & N/A & Apple ARKit & N/A \\ \hline
2019 & [206] & N/A & Google Tango Project SDK & N/A \\ \hline
2019 & [212] & C\# & ARKitTM API tool, Unity3D & 3 ds MaxTM software, Solidworks \\ \hline
2019 & [213] & C\# & Unity3D, Vuforia & Solidworks, 3 DsMax, Rhino3D \\ \hline
2019 & [218] & N/A & MoCap Studio, ARToolkit & N/A \\ \hline
2018 & [65] & C++ & Unity3D & N/A \\ \hline
2018 & [66] & C++ & Unity3D, ARToolKit & 3D Studio Max \\ \hline
2018 & [67] & C/C++ & ARToolKit, OpenGL, VRML toolkit & N/A \\ \hline
2018 & [84] & C\# & Unity3D, Vuforia & N/A \\ \hline
2018 & [94] & N/A & AR Toolkit, & Solid Edge \\ \hline
2018 & [108] & C\# & Unity3D, HoloToolKit & N/A \\ \hline
2018 & [109] & N/A & Microsoft Visual Studio, OpenCV & Coin3D \\ \hline
2018 & [121] & C++ & OpenCV, OpenGL, Matlab & N/A \\ \hline
2018 & [153] & C\# & Unity3D, Vuforia & N/A \\ \hline  & & & Leap motion control, VST AR architecture, & \\ \hline
2018 & [167] & N/A & Visual Studio, & N/A \\  & & ARToolkit libraries & & \\ \hline
2018 & [176] & C\# & Unity, Vuforia & Catia \\ \hline
2018 & [214] & N/A & OptiTrack, ARUCO library & N/A \\ \hline
2017 & [86] & C\# & Unity3D, Vuforia & N/A \\ \hline
2017 & [99] & C\# & Unity3D, Vuforia & N/A \\ \hline
2017 & [143] & C\# & Unity3D, NET libraries, Vuforia & Catia \\ \hline
2017 & [144] & C\# & Unity3D, Vuforia & N/A \\ \hline
2017 & [152] & C\# & Unity3D, Vuforia & N/A \\ \hline
2017 & [199] & C\# & Unity 3D, Vuforia & N/A \\ \hline
2017 & [200] & C\# & Visual Studio, OpenCV & N/A \\ \hline
2017 & [223] & C\# & Unity3D, Vuforia & N/A \\ \hline
2016 & [125] & N/A & COLLADA, ARToolkit & SolidWorks \\ \hline
2016 & [131] & C\# & Unity, Vuforia & N/A \\ \hline
2016 & [132] & C\# & Unity, Vuforia & N/A \\ \hline
2016 & [145] & N/A & OpenNI (cross-platform framework dedicated to Natural Interaction), OpenCV, ARToolKit & N/A \\  & & & library, OpenGL, OpenSceneGraph (OSG) & \\ \hline
2016 & [168] & N/A & OpenGlj, ViSP tracking platform (Visual Servoing Platform) & N/A \\ \hline
2016 & [158] & C\# & Unity3D, Vuforia & N/A \\ \hline
2016 & [171] & C++, Java & Visual Studio, OWL API & N/A \\ \hline
2016 & [177] & C\# & Unity3D, Vuforia, ROS, JSON library & N/A \\ \hline
2016 & [179] & N/A & Unifeye SDK, Metaio platform & N/A \\ \hline \hline \end{tabular}
\end{table} 
Table 16: _Cont._RQ4: How can AR-based applications for quality sector be evaluated? Layer 3 consists of two main categories, which are effectiveness evaluation and usability evaluation. While effectiveness evaluation technically considers evaluation metrics such as completion time, the number of errors, productivity performance and other quantitative key performance indicators (KPIs), usability evaluation concentrates on the study of the user experience via interviews, questionnaires and field evaluations, as well as utilizing expert evaluations of the AR systems. As the complexity of tasks and AR systems has evolved over time, a hybrid evaluation of effectiveness and usability should be applied to holistically consider all impact factors that could help for the improvement of the investigated AR system. In terms of effectiveness evaluation, quantitative methods such as descriptive statistics, t-test and analysis of variance (ANOVA) were applied in several studies included in this SLR [92, 188, 195]. Regarding usability evaluation, two standard questionnaires, which are NASA Task Load Index (NASA-TLX) and the System Usability Scale (SUS), are usually utilized [194, 220]. The NASA-TLX questionnaire is widely used to evaluate physical and digital experiences in working environments. The SUS questionnaire is short, concise and