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1. Introduction
Statistical process control (SPC) is a set of procedure utilizing statistical techniques to improve the quality of products or services, and the main objective is to measure and analyze the variation in processes. Since the 1970s it is widely used in the entire industry environment (Gaafar and Keats, 1992). Manufacturing and service platforms have benefited from the SPC tools in the various situations. SPC methodology has been used to identify the root of causes in process variations as either a common cause or a special cause. One of the advantages of SPC is its ability to detect quickly any special cause variation or process shift event so that the process can be inspected and corrective action can be taken before the quality deteriorates and any defective product is produced (Jiang et al., 2007). Montgomery (2005) specified SPC as a powerful collection of problem-solving tools helpful in realizing process stability and improving performance and capability through the decline of variability. SPC methods and principles have been described also in the framework of service industry by Deming (1986), who has aimed his quality philosophy on all the processes, including services. Later, Rosander (1991) investigated and set out a practical application of Deming philosophy for services. Amsden et al. (1991) provided an introduction to statistical techniques that are applied to measurements in service processes. In literature, successfully sustained implementations of SPC in service processes are scarce. First significant application of SPC in the service sector has been used by Roes et al. (1997). They considered services where quality of service provided is mainly judged through the consumer response. Control chart is one of the SPC tools that is mostly used in manufacturing environment, however, Saniga (1997) and Montgomery (2005) used control charts and extended them in many non-manufacturing and service environments. In the service sector, control charts have been propound and applied in healthcare by Benneyan (1998) and Kelley (1999). They used continuous quality improvement to make use of professional techniques such as customer satisfaction evaluation, supplier quality evaluation, statistical quality and processes control analysis, competitive benchmarking and supply chain management to improve the quality of system in the health care service. Jiang et al. (2007) developed an SPC framework for activity monitoring in...