# Investigation of Interactive Strategies Used in Undertaking Collaborative Tasks
## 4 Experiments
### Experiment I: Tele-Operation vs. Tele-Assistance7  
This experiment investigated the task performance of the two interactive strategies--Tele-Operation and Tele-Assistance7, respectively. Participants: There were a total of 22 participants (assuming the role of the novice) between the ages of 20 and 30 years old, more than the minimum sample size (11) determined from the pilot test. All participants were naive to the purpose of the experiment, possessed normal or corrected-to-normal vision with a stereo acuity of at least 40\({}^{\circ}\) arc (determined by using the Randot Stereotest), and had no difficulty in recognizing colors under the Ishihara color-blindness test. As ascertained by using a modified version of the Edinburgh Handedness Inventory [22], they were all strongly right-handed for holding the stylus of the haptic device while performing the task. Procedure: To decrease the variability among the participants and to counterbalance the inter-effect between both interactive strategies, we adopted a within-participant, cross-over design for the experiment. That is, half of the participants undertook the collaborative task under the Tele-Operation format first and then under the Tele-Assistance7 format, while the other half of the participants performed the task in the reverse order. Under one interactive strategy, each participant underwent six sessions. As a practice session, the first session allowed the participant to become familiarized with the CVE and his/her role in the collaborative task. This session used the object of Shape ID: 6, as depicted in Figure 3, as both target and manipulator objects. The rest of the sessions consisted of five testing sessions to record raw data for computing all performance parameters. In each testing session, one of the objects from Shape ID: 1 to Shape ID: 5, as shown in Figure 3, functioned as both target and manipulator objects. The order of the testing sessions was randomized under each interactive strategy. The use of the six objects decreased the chance of the participant remembering previously viewed manipulator objects, since humans have a short-term memory capacity of approximately four items [23]. In each session, the manipulator object was randomly placed some distance away and reoriented from the starting point. Upon having finished all testing sessions under one interactive strategy, the participant completed a NASA-TLX questionnaire [20] to assess his/her perceived workload of the task. Each participant engaged in the experiment for approximately 1.5 h, including the time needed to complete the NASA-TLX questionnaire. The order of the two interactive strategies was counterbalanced for all participants. Data analyses and results: Data analyses used the Wilcoxon-signed-rank test to examine whether the interactive strategies have any significant effect on each performance parameter. A _p_-value less than 0.05 indicated a statistical significance, as in most studies on human performance. On average, the participants took less time to complete the collaborative task under Tele-Operation (4.88 \(\pm\) 0.07 min) than under Tele-Assistance7 (7.85 \(\pm\) 1.90 min), as shown in Figure 5a. The difference of the completion time between Tele-Operation and Tele-Assistance7 was statistically significant (Z = \(-\)4.107; \(p\) < 0.05). As illustrated in Figure 5b, the participants made more accurate operations under Tele-Operation with an error of 0.037 \(\pm\) 0.002 cm, compared to under Tele-Assistance7 with an error of 0.065 \(\pm\) 0.004 cm. A Wilcoxon-signed-rank test confirmed the observation that the participants under Tele-Operation were able to attain a greater degree of precision than under Tele-Assistance7 (Z = \(-\)4.010; \(p\) < 0.05). On average, the participants took a greater number of operations under Tele-Operation (33.10 \(\pm\) 1.51 steps) than Tele-Assistance7 (22.15 \(\pm\) 1.22 steps), as revealed in Figure 5c. This difference of moves was statistically significant too (Z = \(-\)3.913; \(p\) < 0.05).