Deming's Funnel Experiment In Quality Improvement

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Deming's Funnel Experiment In Quality Improvement - A Computer Simulation

Mohamed M. Mostafa

Abstract

inconsistencies, there is variation introduced due

to people, materials, and the environment. Consequently, the measured quality of a manufacture's product is always subject to a

The funnel experiment was designed by Dr. WE.

Deming to show managers several lessons in management and in quality improvement. Surprisingly very little is known about the statistical properties of the funnel experiment. We simulate the experiment to evaluate the strategies proposed by Deming to adjust the

certain amount of variation as a result of chance. We refer to this situation as a stable

system of chance causes of variation. Variation

within this stable pattern is random and

The main morals of the funnel funnel. experiment for management are that variation is to be expected in any process owing to numerous random factors and that therefore punishing or

inevitable. Variations outside this stable pattern is another matter. Once discovered, causes for such variation (called assignable causes) should be searched out and corrected. Detection of such variation is a key objective of quality control.

rewarding workers is both futile and wrong. Based on Deming's funnel experiment, we should differentiate the management tasks in dealing with variability when it is partitioned

For a production process, one of the goals of a quality improvement programme is to reduce the variability in the process, with an eye toward eliminating this process variation: an impossible task, but a goal nonetheless. By keeping a close watch on process variation and not over reacting to chance variation, a company can bring about dramatic improvements in product quality and a reduction of spoilage and rework. This can be

into special cause variability and common cause

or inherent variability. The work on the reduction of special cause variation needs to

continue to focus on process control, on quality

assurance and especially on training and compliance.

Introduction \V. Edwards Deming spent his life's career in the field of quality management and is often associated with total quality management (Peterson, 1999). Today Deming is generally regarded as the top leader in quality management, and is still cited as the founder of

illustrated in a very striking and entertaining way

using a favorite device of Deming - the funnel experiment.

The Deming Funnel Experiment

The funnel experiment was often used by

the third wave of the Industrial Revolution (Brocka and Brocka, 1992).

Deming in his lectures to illustrate that reacting

A major point made by Deming was that

effect on overall process variation. Despite the good intentions of a machine operator to 'fix"

to chance (random) variation has an adverse

variation is the enemy of quality (Neave, 1996). Variation exists in every process and in nearly every sample of measurements. Even the best automatic machine tools cannot make every unit Along with machine exactly the same.

the system and move it