## 3 Empirical Studies
### Experiment Results  
Table 3 summarizes the experimental results, such as the number of activated sensors and the accumulated volumes of disposals. The experiment was conducted by the randomly generated orders shown in Table 1 in the Appendix. For example, see trial 1 in group 1. Here, 3 (47%) means 3 sensors were activated at 47% full collection box. The results were recorded as soon as the sensor was first activated and continued until the accumulated volume of disposals was increased to 70% full for experimental reassurance. It was twice observed that the number of activated sensors decreased because the empty space between the disposed of e-wastes at the collection box was reduced. Also, the number of activated sensors was not changed, even though new disposal of e-wastes into the collection box occurred, due to the existence of sufficient empty space in the box. It was also observed that the number of activated sensors of each trial in the same group could be different. The reasons are identified as the empty space between the disposed of e-wastes and the disposal locations in the collection box. It was observed 21 times that the lid of the collection box was not closed properly. Also, the first activation of the sensor was observed at different accumulated volumes of disposals at the collection box in the range (38 to 59%).  
A total of 409 events of sensor's activation with 100 trials (20 groups) were observed through the experiments while new e-wastes were disposed of into the collection box. In other words, each scenario was repeated 5 times due to the randomness of the empty space between e-wastes. Also, a total of 94 trials were observed when more than 2 events occurred in each trial. In addition, the first event with less than 6 activated sensors was counted in 73 trials. With another 6 trials, only one event was observed within a trial. Table 4 summarizes the experimental results with the number of activated sensors and accumulated volume. For example, in the first trial of group 2, three events were recorded with different numbers of activated sensors (accumulated volume of e-waste): 6 (54%), 10 (58%), and 16 (64%). On the other hand, in the first trial of group 3, five events were recorded with results of 1 (38%), 3 (41%), 6 (47%), 8 (54%), and 12 (60%).  
As can be seen from Table 3, for all the 18 events of an unclosed lid of the collection box, it was observed that the accumulated volume of disposals was over 60% full. Therefore, it is statistically identified that collecting the disposed e-wastes from the collection box is efficient whenever an unclosed lid occurs. Next, Figure 9 shows the marginal plot of the number of activated sensors according to the accumulated volume of the disposed e-wastes in order to identify the proper collection algorithm. In the case when the number of activated sensors is more than 11, all other events happened when the accumulated volume was greater than or equal to 60% full.  
Among the 164 events when the number of activated sensors was less than 6, a total of 73 events were observed when the accumulated volume was less than 58%. That means that well-balanced disposals into the collection box happened 85.98% (=141/164) of the time. By considering that the disposals of e-wastes into the collection box follow the latent process, the increment of activated number of sensors is very important for developing the collection algorithm.