When will I ever need to use Venn Diagrams?

This is a fun one. I have liked the idea of using Venns for work, but for technical people, they are typically too high-level (i.e. they summarize something obvious).

So my oldest came home and had me review his homework of Venns. Since "I'll never use this" has become a disappointing game for him, he asked if I used these today. I thought about it and said, "No". But I did mention that I have used them in the past.  He left happy.

The next morning before he went to school I had an early morning meeting, and ended up needing to review a document of product failure precipitation techniques (processes to simulate aging effects and find poor design or manufacturing errors). 

At the top there was a Venn diagram that not nearly as complicated as this one (but more proprietary):

sad face
That was not a happy morning for my son, since he's trying negotiate his way out of fancy math by saying he'll never use this stuff.

Credits:
http://kinnechapin.com/tag/listography/ for the simple Venn
http://www.collegehumor.com/article/5778557/venn-candygram for the candy Venn
http://en.wikipedia.org/wiki/File:Symmetrical_5-set_Venn_diagram.svg for the fancy Venn

When will I ever need to use ______ ?

xkcd.com

One of the pleasures of being an engineer parent is when your kids come home with math homework.  It's an opportunity to flex parts of your brain that haven't been exercised in decades. (Never mind the depression/anger that arises when the teacher gives the parent a bad grade.)

But it gets even better when you are able to tell them that this ridiculous concept that they're learning really can be used in real life, if they get into certain professions.

This series will be a journey of answering the question, "When will I ever need to use         ?". It will be populated by real life examples that I encounter during the course of my job and my sons' math-lete adventures.