# The Human-Centredness Metric: Early Assessment of the Quality of Human-Centred Design Activities
## 3 Results
### Improving the Human-Centredness Metric (HCM)  
Since the applicability, consistency, and structure of the HCM are also to be further improved, further statistical investigations are carried out for this purpose. Firstly, an overview is given of those items whose application was not possible in every case and were therefore rated as \"not applicable\". As the diagram in Figure 7 shows, this occurred particularly with items from the areas of usability and user experience, whereby all but one of these items from the user experience category can be assigned to the visual aesthetics evaluation (User Experience No. 6-12). This indicates the need for the refinement of item phrasing, with particular attention to improving the user experience evaluation, especially in the area of aesthetics evaluation. Likewise, another measure of the applicability of the metric is the number of items that achieved complete fulfilment in all 16 concepts, meaning that they had no effect on the total HCM score. This is the case for Usability No. 12, User Experience No. 4, Accessibility No. 7, and Avoidance of Use-Related Damage No. 1, 3, and 4. This also indicates that the items were formulated too imprecisely and thus were always marked as probably fulfilled. To check and improve the internal consistency of the items, the value of Cronbach's alpha [67] is calculated. In all 16 cases and a total of 54 items, the value is a = 0.830, which can be interpreted as a \"good\" value. The detailed evaluation shows that this value can hardly be improved by omitting individual items. By omitting one of the items Usability No. 16, 18, or 21, User Experience No. 3, or Avoidance of Use Related Damage No. 5, 6, 8, or 9, a maximum alpha value of up to a = 0.835 could be achieved. This does not seem to be a large effect, but should be investigated again in future experiments with a larger sample. Finally, the question remains as to whether the division of the HCM into more defined and non-overlapping factors is possible. The initial categorisation into four groups--usability, accessibility, user experience, and avoidance of use-related damage--proved valuable in developing the metric initially. However, this approach occasionally results in the dispersion of related topics, such as ensuring safe operation, across multiple categories. This can be improved with the help of a factor analysis. To begin, the number of relevant factors must be determined. It depends on how much variance of the item correlation can be explained by the individual factors. The explained variance per factor corresponds to its eigenvalue, whereby all factors with an eigenvalue >1 are to be considered according to the Kaiser-Guttman criterion [68; 69]. Based on this analysis, the 54 items should be allocated across 11 factors, collectively accounting for 93.6% of the variance in all variables. While the cumulative variance is notably substantial, the 11-factor allocation might appear relatively extensive. Therefore, we further wish to examine the scree plot. Figure 7: Frequency of items marked as “not applicable”. According to the scree test [70], the eigenvalue plot is examined for a \"kink\" and the number of factors is selected whose eigenvalues lie above the kink. In our case, these are six factors (Figure 8, red horizontal line). We decide on six factors accordingly and sort the items that have the highest loadings for the six factors in each case. If an item has a similarly high loading for more than one factor, these are assigned to the most suitable factor in each case according to their meaning and not their loading. The same applies to the six items that cannot be evaluated in the factor analysis due to their 100% degree of fulfilment, i.e., Usability No. 12 (USA_12), User Experience No. 4 (UEX_4), Accessibility No. 7 (ACC_7), and Damage Avoidance No. 1, 3, and 4 (DAM_1, DAM_3, DAM_4). This results in the following six factors with their respective items. For better traceability, the abbreviations of the original sorting have been added for each item. 1.