Canadian Plastics

Pareto problem-solving

In the 20th century, there were two gods of quality assurance: Drs. Edward Deming and Joseph Juran. Everyone knows about Deming, but Juran is often overlooked...although he shouldn't be. Juran focussed on the management approach to quality, but...


September 1, 2009
By Jim Anderton, technical editor

In the 20th century, there were two gods of quality assurance: Drs. Edward Deming and Joseph Juran.

Everyone knows about Deming, but Juran is often overlooked…although he shouldn’t be. Juran focussed on the management approach to quality, but one of his most important contributions was his discovery — or more accurately, rediscovery — of Italian economist Vilfredo Pareto.

An economist? Yes! Juran’s application of Pareto is the origin of the principle that 80 per cent of a problem is created by 20 per cent of the causes. Juran called this principle “the vital few and the useful many”, to remind us not to forget about the other 20 per cent.

Interesting, but why should we care? Well, one application of Pareto’s work is the “Pareto diagram”, a very simple, very powerful tool for tracking down problems. Here’s how it works:

1 Classify the different types of non-conformity or failure into groups, then label them, say, “A” through “G”. Put this on the horizontal line of a regular bar chart, spreadsheet or paper.

2 On the vertical axis, put dollar cost of non-conformities or simply the number of non-conformities. I like both, on separate charts.

3 Collect the data and group it by the type of non-conformity and then assemble the bars of the graph.

Voila

The beauty of the Pareto method is that it’s simple and visual; there’s no massaging the data with mathematics, and no ambiguity about the hot problems. Another bonus is that non-technical personnel can draw it up…as long as the initial classification of the failure types is established; the rest is just counting the non-conformities. It can be as simple as making a series of labelled boxes and having inspectors put the bad parts in each box. Each box’s contents make a bar of the chart.

And there’s another, hidden benefit: you don’t have to use it for production only! You choose the failure classifications; it could be order entry mistakes, missed phone calls, or the amount of toilet paper used in each washroom, but the principles are the same.

It’s faster to do it than explain it, so go ahead and make a Pareto chart and play with the values, especially the failure classification types. You may surprise yourself! CPL