Deming’s funnel experiment in quality improvement – a computer simulation

The funnel experiment was designed by Dr W.E. 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 funnel. The main morals of the funnel experiment for management are that variation is to be expected in any process owing to numerous random factors and that therefore punishing or 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 into special cause variability and common cause or inherent variablility. 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.