## 2 State of Art  
### Studies on Customer Satisfaction Evaluation  
Research on employee satisfaction is more prevalent in the literature than studies on customer satisfaction, covering sectors such as healthcare [7; 8; 9; 10], tourism [11; 12], call centers [13; 14], and banking [15; 16]. Although customer satisfaction has been addressed in various studies, only the study by [PERSON] et al. [17] has explored this in the context of water laboratories. In their study, the authors evaluated customer satisfaction levels in water laboratories accredited to TS EN ISO/IEC 17025 using a ten-question questionnaire with a five-point scale. The results showed an average score of 4.83 \(\pm\) 0.07, equating to 96.6% satisfaction. The study concluded that customer satisfaction was higher for these accredited laboratories, leading to corrective actions to improve services [17]. [PERSON] et al. [18] conducted a study examining the impact of service quality on customer satisfaction in an ISO/IEC 17/025:2017 accredited calibration laboratory in West Sumatra, considering the moderating roles of organizational culture and price. The study found that service quality is crucial for customer satisfaction, which, in turn, can drive economic improvement. Data were collected from 93 respondents representing government agencies and private companies in West Sumatra through questionnaires. The data analysis revealed that service quality has the most significant impact on customer satisfaction, suggesting that organizations that enhance the quality of their services can significantly improve customer satisfaction. Additionally, organizational culture has a significant influence on customer satisfaction, with improvements in poor organizational culture leading to a major positive effect. The price of services also plays a significant role in customer satisfaction; transparent, reasonable pricing based on legal standards can build customer trust, further enhancing satisfaction. However, the study found that the moderating effects of organizational culture and price do not significantly alter the relationship between service quality and customer satisfaction. [PERSON] et al. [19] discuss the importance of a laboratory quality management system for the effective operation of research, clinical, testing, or production/manufacturing laboratories. According to the authors, maintaining a robust laboratory quality management system is critical for managing a variety of laboratory activities, including basic and applied research, regulatory and clinical testing, and proficiency testing, as well as for ensuring records management and continuous improvement. This system provides a framework to identify and mitigate gaps and risks throughout the laboratory workflow, helping to prevent critical errors that could undermine the integrity and credibility of the institution. It ensures that results and data are reliable, accurate, timely, and reproducible. The authors explore different laboratory quality management system framework options suitable for various laboratory categories and discuss the necessary considerations for their implementation. They demonstrate that a laboratory quality management system that properly integrates all relevant requirements, promotes risk-based thinking, and addresses the entire laboratory workflow can ultimately lead to the generation of high-quality and relevant data. Such a system fosters greater confidence in the quality of data and results, encourages best practices, and cultivates a culture of responsibility and safety within the laboratory. A study conducted by [PERSON] and [PERSON] [20] aimed to apply lean six sigma in a water testing laboratory to enhance efficiency, operate effectively in a lean environment, improve customer satisfaction, and reduce customer complaints. Lean six sigma offers a comprehensive approach to process improvement and is applied across various industries to boost operational efficiency and the quality of products or services.