Considering the complex nature of how customers judge service quality, a number of researches have been done in the area and models have been developed to explain the nature of service quality evaluation.
1. Gap Model: The definition of high quality is neither static nor identical in every situation.
Parasuraman, Zeithaml, and Bitner identified four potential gaps within the service organization that may lead to a final and most serious gap.
The difference between what customers expected and what organizations perceived is a known gap in service quality.
2. SERVQUAL Model: The SERVQUAL model was developed by A. Parasuraman and colleges in the USA.
SERVQUAL is based on the expectations disconfirmation approach known as the disconfirmation paradigm.
The model of service quality, which they made, identifies the reasons for any gaps between customer expectations and perceptions.
3. Critical Incident Model: The critical incident study technique is used to improve customer care. It is relatively simple and cost-effective for implementation.
A critical incident is a defining, special, problematic, unpleasant, or even delicate incident, which affects the customer perception of the quality of service.
4. SERVPERF Model: SERVPERF, the performance component of the Service Quality scale (SERVQUAL), has been shown to measure five dimensions corresponding to Tangibles, Reliability Responsiveness, Assurance, and Empathy (Parasuraman, Zeithaml & Berry).
5. Gronroos’ Perceived Service Quality Model: In Gronroos Perceived Service Quality model, expectations are a function of market communications, image, word-of-mouth, and consumer needs and learning, whereas experience is a product of a technical and functional quality, which is filtered through the image.