Discerning Signal from Noise using Italian Peas

What's important? What demands our attention, and what can be relegated to the back burner?


In engineering, when we talk about discerning what's important from what is not, we use the terms signal and noise. For a long time in human history, determining what was important was trivial. Food, shelter, survival - these were the important things. Then we started creating and living in complex systems, and the ability to discern the signal from the noise became non-trivial.


But here we are, immersed in complexity, and in need of some tools to help us understand where to put our energy. One of those tools we teach in Lean Six Sigma is the Pareto chart. Many people are familiar with the Pareto principle, or the 80/20 rule that states "80% of effects come from 20% of causes." There have been a lot of misapplications of this 'rule' in the past century since it was first articulated, but the basic principle of non-linear cause-and-effect is repeatedly observed in complex systems. The principle is named for Vilfredo Pareto, an Italian engineer turned philosopher, who reportedly noticed (among other things) that about 80% of the peas in his garden came from 20% of the pea pods.


The Pareto chart is named for Vilfredo, but he didn't invent it or use it. Essentially it's a bar chart with some very specific rules. The most important rule is that bars are arranged from tallest to smallest, left to right. It is used widely in quality control to associate root causes with defects. In this form causes are categories on the x-axis, and effects are counts of defects on the y-axis. Visually, the 20% (roughly) of causes that cause 80% (roughly) of the effect are the 1 or 2 bars on the far left. It might look something like this:


But here's another way of thinking about that: the categories on the left are signal, and everything else is noise. In other words, in studying cause and effect, the Pareto chart gives us a means for discernment. We can't give all sources of pain the same level of attention, because when everything is important, nothing is important. Instead we can put most of our energy on the signal that's buried in the noise. Visually it looks something like this:

You might find that you can use this principle outside of the mundane world of statistical process control. In your life, there are probably dozens of things pulling at you for your attention at any given time. But in any complex system (including your life) there are probably a smaller number of things (like 20%) that actually demand your attention. How many things can any person spend their attention on, anyway? Well according to research, that number is seven, plus or minus two.


This is potentially liberating science. It means that 80% of the things you worry about are probably noise. 80% of the things that occupy brain cycles with worry and consume energy will never amount to anything. I'm serious. 80% of Italian peas can't be wrong.

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