Continuous Process Improvement with Observational Studies

Abstract

The essential feature of an observational study performed on a process is that data are collected without deliberately changing the process. Control charts, a type of observational study, have traditionally been used to establish and maintain process stability. Once stability is achieved, charting controls the process variability but does not reduce it further. This paper proposes the use of charting techniques in conjunction with observational studies for continuous variation reduction, that is, continuous improvement. The basic strategy is to devise a sampling design that identifies the largest sources of variation. Then as improvements are made, the sampling designs and corresponding analysis methods are updated. Consequently, most of the charting effort becomes an off-line activity. The necessity of up-front planning is also discussed.

• Graphical Methods
• Sampling Designs
• Sources of Variation

Additional information

Notes on contributors

M. Hamada

Dr. Hamada is a Research Assistant Professor in the Department of Statistics and Actuarial Science and The Institute for Improvement in Quality and Productivity. He is a Member of ASQC.

R. J. Mackay

Dr. MacKay is an Associate Professor in the Department of Statistics and Actuarial Science and The Institute for Improvement in Quality and Productivity.

J. B. Whitney

Dr. Whitney is an Associate Professor in the Department of Statistics and Actuarial Science and The Institute for Improvement in Quality and Productivity.