# The Human-Centredness Metric: Early Assessment of the Quality of Human-Centred Design Activities
## 2 Materials and Methods
### Experimental Design
As part of the approach, participants always had to write requirement lists and function structures and build morphological matrices, additionally to creating concepts for the task given. Disturbance variables and other variables. The students had up to four hours to work on each of the assignments and were allowed to take breaks at their own convenience. Each assignment consisted of a task description including an objective, hints, and pictures of three sample products. There was no additional information about the sample products given to the students, and no technical drawings or function descriptions. Except for the objective and the sample products, the task descriptions were identically phrased for each assignment, regardless of the product to be designed. For example, the objective in the case of the coffee machine assignment was \"Find new, innovative, and user-friendly concepts for a coffee machine resp. the main function of making coffee\". The objectives for the other products were formulated analogously. In addition, the students were advised in the hints that they should focus primarily on parts and functions in the product concept that were in direct interaction with the operator or were noticed by him/her. This experimental design and task setting were intended to keep disturbance variables and other variables under control as far as possible. Design of the independent variable. The goal of a controlled study environment was found to be challenging with regard to the selection of human-centred design methods. In the case of most approaches, we found it difficult to conduct them under the same boundary conditions or in the form of a simulation. Interviews or focus groups are difficult to simulate without user interaction, but a real or simulated user interaction seemed to be a major disturbance variable. The presentation of, e.g., simulated questionnaire data also appeared to us to move beyond the time frame of the study, as only half a day could be planned per session and the evaluation and interpretation of user data can be quite time-consuming, especially for inexperienced designers. Therefore, the human-centred approaches had to be selected or prepared in such a way that they could be conducted alone by the student, without direct end user interaction, and that they could be understood and applied within a few hours. In order to minimise learning effects in the course of the sessions, three different methodological approaches were chosen that were as different as possible in terms of their goals or approaches. The Principles of Universal Design (M1) [48], the Persona Scenario Method (M2) [62], and the Dialogue Principles (M3) [63] were selected here. Although these three are not equally mature design methods--in the case of the guidelines, they are rather tools--they are nevertheless applicable in the context of early product development and still met our further requirements by far the best. For each, a method profile was prepared. It consisted of a short summary of the basic idea and goals as well as the procedure of the method. In addition, the reference papers were provided. The Universal Design Principles (M1) are a set of guidelines or best practices about designing products, buildings, and information in such a way that they can be used by as many different people as possible without restriction or the need for adaptation [48]. Universal Design is thus intended to increase the accessibility of products. There are a total of seven principles, such as Equitable Use, to which several guidelines are assigned. The principles can be integrated at various points in the development process. In the Persona Scenario Method (M2), one or more personas undergo one or more interaction scenarios; as a result, new insights about the user and the interaction as well as design ideas will result [62]. This method thus can enhance the user experience for the user. Personas are fictitious characters with detailed descriptions of many different attributes, e.g., age, occupation, and consumption habits.