# The Human-Centredness Metric: Early Assessment of the Quality of Human-Centred Design Activities
## 4 Discussion  
The evaluation with the HCM shows patterns and trends with regard to better human-centredness when using additional methods that can be assigned to the area of human-centredness in the broadest sense, in contrast to not using any additional method. This also corresponds to our definition from Figure 1 that activities that take place without direct user interaction but provide information about the user or the context of use are also to be defined as human-centred, since they are capable of improving human-centred design quality goals in the design. Due to the lack of significance of the results, however, this answer cannot be given conclusively. The results seem to be independent of other influencing factors examined, such as the choice of product examples, the order in which the experiments were carried out, and the abilities of the students, as we deliberately mixed these factors within the design of the experiment, although it is also difficult to give definitive answers here. However, other measurement methods that were used comparably early in the design process, as in [PERSON] et al. (2015), turned out to be quite applicable and usable too. We therefore assume that the weakness lies more in the experimental design than in the basic idea of the metric. However, this was primarily designed to test the internal consistency and suitability of the HCM for an appropriate task.  
Apart from the limitations already mentioned and partly addressed in the experimental design, the early stage of development of the concepts is a further one. Thus, only those functions could be evaluated by the metric that were also expressed in concrete terms by the participants. In the case of the vacuum cleaner, for example, one student described the changing of brush attachments, but the description of other basic operating processes, i.e., switching on/off, adjusting power, etc., was largely neglected; these could not be evaluated or could only be anticipated to a limited extent from the requirement and function lists. Nevertheless, even in the case of missing or insufficient descriptions, decisions were usually made in favour of the concepts. It is therefore possible that with increasing detail and repeated application of the evaluation at a later point in time, the scores in the HCM will decrease and the concept may be found to be less user-friendly or less accessible than previously assumed. Accordingly, it is not possible to choose the most user-friendly, most accessible, etc., concept with high probability at this very early development stage.  
There are also weaknesses in the metric in terms of its applicability and meaningfulness, as can be seen from the overview of items that were partially not applicable (Figure 7), as well as the fact that some items were always fulfilled by all concepts. On the one hand, the items on visual aesthetics in particular reach their limits when they are applied to very early product development phases and thus very rough product concepts. Furthermore, the items on the avoidance of use-related damage show obvious weaknesses in their applicability to the example of household appliances. After all, these items were primarily derived from the Machinery Directive. Larger masses or forces from which a hazard could emerge, however, are generally not to be feared in the case of household appliances. The extent to which this is a problem for the meaningfulness of the metric as such remains open.  
In the context of the product examples used, there is another possible limitation for the HCM. Within the study, it was only applied to physical everyday devices and not to digital user interfaces. Due to the form of the HCM and the topics that it addresses, we assume reduced applicability or a necessity for adaptation for application to purely digital systems. For example, all items that stem from the prevention of use-related damage, as well as some others, are very strongly oriented towards physical devices and can only be logically applied to them.