## 4 Discussion
It should also be noted that sample sizes used in this preliminary study were small and further studies with larger sample sizes are needed to confirm the results of this work. Although the pattern of variations in the distal normalized force peaks was consistent among participants, the absolute value of this measure or the amount of reduction in it with an increase of three sock plies was not the same in all participants. The high inter-participant variability of force measurements is likely due to factors such as user's body weight and their socket fit. As also reported in other studies [31], variability in such participant-specific factors affects the distribution and magnitude of socket-limb interface force/pressure. For example, the load supported by the prosthetic socket would be higher for an individual with higher body weight. This would lead to a higher total socket-limb interface pressure. This study did not identify a consistent relationship between the number of sock plies and the distal force. The results showed that there is a monotonic relationship, but it is individual-dependent as there is a high inter-participant variability in force measurements. In addition, the fact that each amputation and each socket are different from the other makes it difficult to generalize the results with a specific relationship at this point. In fact, as shown in Figure 5, adding one sock ply in one individual has a different effect compared to adding the same number of plies to another individual. Information from a larger population including a number of parameters such as body weight,circumference of the limb, height, location of amputation, shape of the socket, and others in future work may lead to the identification of a relationship that can be generalized across multiple individuals. The small sample sizes used in the two phases of this study are amongst its limitations and lead to low powers of statistical tests, resulting in higher probabilities of making type II errors. However, when significance is determined, one does not need to worry about type II errors as they only occur when significance cannot be determined [32]. The \(p\)-value obtained in the statistical analysis performed in this phase was marginal (\(p=0.049\)) which might be due to the high probability of type II errors which prevent rejection of the null hypothesis when it is false. Results of this analysis should be confirmed in future studies with larger sample sizes. As a result that the significance was not determined in the one-ply phase, statistical analysis was not valid for this phase as its results might have been compromised by type II errors. Thus, results of statistical analysis of the one-ply phase were not reported. Results of the one-ply phase should only be considered quantitatively and need to be confirmed by future studies with larger sample sizes. Although more accurate types of pressure/force sensors, such as load cells, could be used towards the goal of this study, these sensors would result in a costly system which was not aligned with the objective of this work. As confirmed by results reported in the manuscript, FSRs, despite their non-linear response and their inferior accuracy of measurement compared to load cells, can be an inexpensive alternative to such sensors and can provide measurements to determine variations in the volume of the residual limb. To use the proposed method in practice, the sensory system should be embedded in the prosthetic socket of users, and data should be recorded continuously throughout the day. In this scenario, an algorithm would be required to detect the walking action during which FSR signals would be used to determine variations in the residual limb's volume. Various methods can be used for detection of the walking action, one of which is the use of classification algorithms. In the case of applications for individuals with disabilities, case-by-case variability is an important factor and should be considered.