From Diana Bouchard:
A toothpaste factory had a problem:
They sometimes shipped empty boxes, without the tube inside. This was due to the way the production line was set up, and people with experience in designing production lines will tell you how difficult it is to have everything happen with timings so precise that every single unit coming out of it is perfect 100% of the time.
Understanding how important that was, the CEO of the toothpaste factory got the top people in the company together and they decided to start a new project, in which they would hire an external engineering company to solve their empty boxes problem.
Six months and $8 million later they had a fantastic solution on time and on budget. They solved the problem by using high-tech precision scales that would sound a bell and flash lights whenever a toothpaste box would weigh less than it should. The line would stop, and someone had to walk over and yank the defective box out of it, pressing another button when done to re-start the line.
A while later, the CEO decides to have a look at the project. No empty boxes ever shipped out of the factory after the scales were put in place...very few customer complaints, and they were gaining market share. "That's some money well spent!" he said, before looking closely at the other statistics in the report.
It turns out the number of defects picked up by the scales was 0 after three weeks of production use. It should've been picking up at least a dozen a day, so maybe there was something wrong with the report. After some investigation, the engineers come back saying the report was actually correct. The scales really weren't picking up any defects, because all boxes that got to that point in the conveyor belt were good.
Puzzled, the CEO traveled down to the factory, and walked up to the part of the line where the precision scales were installed. A few feet before the scale, there was a $20 desk fan, blowing the empty boxes out of the belt and into a bin.
"Oh, that," says one of the workers, "one of the guys put it there 'cause he was tired of walking over every time the bell rang".