# Adaptive Kinetic Scrolling: Kinetic Scrolling for Large Datasets on Mobile Devices
## 4 Experiment
### Determining Threshold for Trigger  
We conducted the following study to determine the threshold value of the clutch time for triggering the AKS: The participants completed a task to find a specific string data in an alphabetically ordered list on the mobile device, and we measured the target distance and clutch time. The study environment was similar to that of the previous experiment. In addition, all the users participating in the pilot study completed two training tasks as well as the earlier experiment. In this study, five participants in the experiment repeated a given task three times each. Figure 5 shows the measured results with a scatter plot. Note that none of the participants overlapped with the users in the pilot study.  
\begin{table}
\begin{tabular}{c c c c} \hline \hline
**Scrolling Type** & **Target Distance** & **Repetition** & **Total** \\ \hline Standard & 200, 400, 600, 800 & 4 times for each distance & 16 times testing for each condition \\ AKS & 200, 400, 600, 800 & 4 times for each distance & 16 times testing for each condition \\ \hline \hline \end{tabular}
\end{table}
Table 1: User study session for participants.  
When the target distance is between 200 and 800, the clutch time measured is approximately 100-200 ms. This is because when the user assumes the current position of the scroll to be far enough away from the target, they scroll rapidly and repeatedly to omit the unnecessary parts. Conversely, if the target distance is near and below a certain distance, the clutch time will increase significantly. The reason for this is that people are aware that they are close to the target and perform the action by examining the change by scrolling. The results from our study were similar to those in [27].  
Based on these measurements, we have determined the threshold for triggering AKS. To determine a threshold, we set up the following two conditions:  
1. Is AKS not triggered when the target is near?
2. Is AKS triggered when the target is far?  
Condition 1 is intended to prevent side effects, and it implies a type of false-positive case. Condition 2 implies precision. These two conditions are in conflict. For example, if you set the threshold excessively low, it can cause side effects if AKS is triggered too easily and the target is in the vicinity. However, if the threshold is unnecessarily large, AKS will not function, and the effect will be lost.  
In our study, we set the threshold value to 250 ms. We achieved this using the clutch time values exhibited by the users at a certain distance. In our study, users recognized in most cases that the target is close when the target distance was less than 100. Simultaneously, the clutch time increased rapidly (see Figure 5). With this value, over 95% of scrolling satisfied condition 1 and over 90% of scrolling satisfied condition 2.  
We observed a notable point related to condition 2. Several users scrolled slowly regardless of the target distance. This is shown in Figure 5; it is evident at the points with clutch times of 300 ms or more regardless of distance. Therefore, it was not feasible to set a threshold that completely satisfied condition 2, and for our experiment, we set the threshold value marginally conservatively.  
The values may have varied marginally depending on each user's preference and language, the GUI of the list, and the device used. For example, the speed of recognition may vary depending on whether the information in the scrolling list is numeric, text, or a certain language. GUI configuration and text size can also affect users. Therefore, this value should be measured for each system to be applied.  
Figure 5: Relationship between target distance and clutch time.