# Design Principles of a Mixed-Reality Shopping Assistant System in Omnichannel Retail
## 5 Experimentation Methodology  
The customer perceptions of the designed system were elaborated by an empirical study performed in a laboratory environment in Germany for five consecutive days in August 2020. Respondents were recruited through random sampling using broadcast messages and open participation calls on social media. Random sampling has several advantages in this context as it helps to ensure that the sample is representative of the larger population being studied. By randomly selecting participants from a population, researchers can increase the likelihood that the sample will accurately reflect the characteristics of the whole population. It further helps to reduce bias in the selection of participants. If the participants are selected using a systematic or nonrandom method, there is a risk that the sample will be biased in some way. For example, if researchers only select participants who are available at a certain time of day, their sample may not be representative of the population as a whole. Random sampling helps to increase the precision of the results by reducing the likelihood that the results will be  
Figure 8: Flow map of the designed system. influenced by extraneous factors. This can provide confidence in the validity of the results and increase the generalizability of the findings. The sample consisted of 35 participants (18 male, 17 female) from 11 different nationalities (16 participants from Germany). Ages ranged between 17 and 38 years old (Mage = 26.68, SDage = 4.25). When asking respondents about their general level of experience with MR devices, approximately half of the sample group (52%) had used an MR device multiple times before or used them regularly. Figure 9 shows the distribution of MR experience among the sample group. Informed consent was obtained prior to the experiment. Due to the COVID-19 pandemic, the data collection procedure strictly followed the general safety precautions. The experiment started with approximately 20 min of interaction with the MR shopping assistant and was followed by a 15 min interview. After finishing, each participant received financial compensation of EUR 15. Participants were assigned to one of two shopping scenarios--\"in-store\" or \"hotel lobby\"--maintaining a gender balance. Except for the short scenario description, the experimental setup, the task, and the selected products were equal for all participants. Users were allowed to ask questions while interacting with the device. The sample group was asked to browse through the experimental setup, which consisted of 13 different products presented on a table in the middle of the laboratory. The products represented a variety of items from three different categories: search products (i.e., pack of coffee beans, pair of sneakers, pack of milk, LED screen, pack of soft drinks), experience products (i.e., pack of beer, video game disk, a bottle of rum, pack of chocolates, a tech magazine), and services (i.e., insurance, law service, business consultancy). Search products referred to tangible items whose quality could be determined before consuming the product, while experience products can only be evaluated after using or consuming the item [77; 78]. Service products were defined as intangible items, such as one hour of consultancy service, represented by company logos printed on physical paper in the experimental setup. The shopping task was based on general browsing, as adopted from the study by [PERSON] et al. [7], where shoppers were not given a predetermined goal to shop for any specific products [79]. The general browsing task created a context where customers utilized the proposed technology to gather information independent of a current need within a specific category [79]. The subsequent interview aimed to gain feedback on the system's design, usage perceptions, and customer experience. The semi-structured interviews lasted between 30 and 40 min after the participants' interactions with the MR shopping assistant. Table 3 lists the four questions addressed to the participants.