A time series approach to quality control

• Main Author: Dittrich, Gayle Lynn
• Other Authors: Ensor, Katherine B.
• Format: Others
• Language: English
• Published: 2009
• Subjects: Statistics
• Online Access: http://hdl.handle.net/1911/13492

One way that a process may be said to be "out-of-control" is when a cyclical pattern exists in the observations over time. It is necessary that an accurate control chart be developed to signal when a cycle is present in the process. Two control charts have recently been developed to deal with this problem. One, based on the periodogram, provides a test based on a finite number of frequencies. The other method uses a test which estimates a statistic which covers all frequency values. However, both methods fail to estimate the frequency value of the cycle and are computationally difficult. A new control chart is proposed which not only covers a continuous range of frequency values, but also estimates the frequency of the cycle. It in addition is easier to understand and compute than the two other methods.