# Movement Time and Subjective Rating of Difficulty in Real and Virtual Pipe Transferring Tasks
## 2 Materials and Methods
### Data Collection and Analysis  
The order of the pipe transferring tasks for each participant was randomly arranged. For virtual pipe transfers, the participants practiced grasping and pinching the virtual pipe, transferring it to another location, and releasing it before performing the first trial. The participants could practice until they were confident that they could complete the pipe transfer. For each of the pipe diameter and distance conditions, the participants performed the transfer twice by reversing the origin and end circles using each of the dominant and non-dominant hands. These trials were not performed consecutively. Instead, they were randomly arranged. For both the real and virtual pipe transfer trials, the participants were instructed to transfer the pipe from the origin to the end. They could adjust their pace so as to put the pipe exactly within the circle of the end.  
The videos of the virtual pipe transfer tasks, shared by the Hololens 2, on a laptop computer were saved for each trial. For the real pipe transfer tasks, videos were taken using  
\begin{table}
\begin{tabular}{c c c c c c c} \hline
**Diameter (W)** & \(\mathbf{d_{1}}\) & \(\mathbf{ID_{1}}\) & \(\mathbf{d_{2}}\) & \(\mathbf{ID_{2}}\) & \(\mathbf{d_{3}}\) & \(\mathbf{ID_{3}}\) \\ \hline
2.2 & 12.5 & 3.51 & 25.0 & 4.51 & 37.5 & 5.1 \\
4.7 & 23.5 & 3.32 & 47.0 & 4.32 & 70.5 & 4.9 \\
6.0 & 32.0 & 3.42 & 64.0 & 4.42 & 96.0 & 5.0 \\ \hline \end{tabular} Note: Unit for W and distance: cm; unit for ID: bit.  
\end{table}
Table 1: Distance (D) and Index of Difficulty for lateral movements.  
Figure 3: Putting (**a**) a real and (**b**) a virtual pipe (photo taken by another Hololens 2 user) in the end circle in the anterior–posterior direction.  
Figure 2: Pinching a real \(\omega\)2.2 cm pipe (**a**) and grasping a virtual e4.7 cm pipe (**b**) at the origin (photo taken by another Hololens 2 user).  
a smart phone. The videos were also stored on a laptop computer. The pipe movement time (MT), from the hand touching the pipe at the beginning to the release of the pipe at the end, was captured via the timer of the videos. In addition to the MT, the participant gave a subjective rating on the difficulty of the task on a five-point scale: 1. easy, 2. somewhat difficult, 3. difficult, 4. very difficult, and 5. extremely difficult.  
For the lateral pipe transfer tasks, a total of 2160 trials were performed. These were comprised of 2 genders, 15 participants for each gender, 2 hands (dominant and non-dominant hands), 2 origins, 3 pipe diameters, 3 transfer distances, and 2 types of pipes (real and virtual). For the anterior-posterior transfer tasks, a total of 720 trials were performed. These were comprised of 2 genders, 15 participants for each gender, 2 hands, 2 origins, 3 transfer distances, and 2 types of pipes.  
We conducted descriptive statistics and analysis of variance (ANOVA) on both MT and subjective rating of difficulty. A pair-wised \(t\) test was performed on the \(\omega\)2.2 cm pipe to compare the difference of the MT and subjective rating of difficulty between the lateral and anterior-posterior transfers. [PERSON]'s multiple range tests were performed for the posterior comparisons of the factors if they reached the \(\alpha\) = 0.05 significance level. Regression analysis was performed to incorporate the gender, handedness, real/virtual, transferring direction, and the ID [2; 3], which aided in establishing the predictive MT model:  
\[\text{MT}=f(\text{gender, handedness, type of pipe, transferring direction, ID}) \tag{3}\]  
The regression analyses of MT were performed using both all the data collectively compiled and separately for each of the lateral and anterior-posterior transfer, type of pipe, and pipe diameter conditions. The ID was calculated using the original [PERSON] definition: \(\log_{2}(2\text{D}/\text{W})\).