## 2 Materials and Methods
### Experiment Variables
#### 2.2.2 Instruction Methods  
Both paper-based and AR-based instructions were created for this study to instruct the individuals on how to properly execute the maintenance activities. Paper-based instructions were provided on a folder of A4 paper, with one page dedicated to every two steps, and were adapted directly from the piston pump's manual. Each step of the paper instructions had photos, written details, and the necessary tools that were required for each step; see Figure 4.  
For the complex task, paper-based instructions spanned 22 pages and included 40 individual steps to carry out. For the simple task, paper-based instructions spanned 14 pages and had a total of 26 individual steps. An example of one participant employing the paper-based instruction method to complete the simple task is shown in Figure 5.  
Figure 4: Example of paper-based instruction for simple task (pump housing maintenance).  
Figure 3: Exploded view of the pump housing (simple task).  
The AR-based instructions were developed using Creo Illustrate and Vufforia Studio software (2019 version) for generating the maintenance steps and the AR experience, respectively. In addition, JavaScript was utilized to create the essential characteristics of AR apps. Figure 6 gives an overview of the implementation of the AR-based maintenance instructions. For displaying the AR instruction, the Vufforia View app stored on the Microsoft HoloLens (1 st gen) was used for scanning specific quick responses (QRs), as shown in Figure 7.  
The 3D animated maintenance sequence was delivered to the participants' surroundings using the first-generation Microsoft HoloLens (Microsoft, 2019), as presented in Figure 8. In this method, participants could experience the digital model interacting with the real environment. For instance, they placed the model in the recognized marker 130 cm away from them on the maintenance desk.  
The interaction technique for the proposed AR application employed head movement tracking, letting users manipulate the maintenance 3D animation sequence using 3D buttons. To trigger the maintenance steps, the users merely needed to move their heads to manipulate a pointer and point to a 3D button. The user could navigate through the  
Figure 5: Participant employing paper-based instructions to complete the simple task.  
Figure 6: Workflow for the building of the AR-based maintenance instructions.  
instruction sequence in the application using 3D buttons to obtain guidance on the current step, move to the next or previous step, and rapidly go to any step. Figure 9 presents an example of one participant performing the complex and simple tasks via the AR method.  
To minimize the impact of varying AR systems and instruction formats on the reproducibility of this study, the experimental protocol incorporated an AR system that is a market leader known for setting industry standards. Additionally, a standardized presentation style for both digital and manual instructions was employed to reduce design variability. However, it is recognized that different AR systems and instructional formats  
Figure 8: AR experience for a complex task.  
Figure 7: Quick response (QR) codes created by PTC software version 9.2.2. Note the hexagonal-shaped QR code, which allowed a device to access the correct augmented reality experience.  
Figure 9: Participant employing AR techniques to complete some steps of the complex and simple tasks.  
could yield different outcomes. Therefore, the results should be interpreted with the understanding that they might vary under alternative conditions, and further research is encouraged to investigate a range of technologies and presentation styles to better ascertain the generalizability of these findings.