Five why is a very powerful method. It’s a logical way to find your root cause. But it can do even more. It can take you on a interesting and maybe funny journey. Most of you probably know the typical (boring) five why example like this one:

1. Why did the machine stop?
   It blew a fuse.
2. Why did the fuse blow?
   The fuse was the wrong size.
3. Why was the wrong size in the fuse box?
   The engineer put it there.
4. Why did the engineer do that?
   The supply room issued the wrong size fuse.
5. Why?
   The stock bin was mislabeled.

Root cause label -> countermeasure to put the right label on.
Good example and easy to understand.

Our kids use the 5 whys root cause analysis daily. We have forgotten this root cause analysis method by just ‘growing up’. But isn’t it still fascinating. Read through this nice story:

1. Daddy, why can the space shuttle fly into the universe?
   Because it has two highly sophisticated world class booster rockets attached to the sides of the main fuel tank to launch it in the sky.
2. But, why are the booster rockets so small in comparison to the space shuttle and the fuel tank?
   Because they need to be shipped by train from their factory in Utah to the launch site and this journey runs through tunnels in the mountains.
3. OK Daddy, but why are tunnel of just this size?
   This tunnels are made for trains and a train is just a bit wider than the railroad track.
4. mmmh. Why is the railroad track that small?
   The US standard railroad gauge (distance between the rails) is 4 feet, 8.5 inches.
5. Why was that gauge used?
   Because that’s the way they built them in England, and English expatriates designed the US railroads.
6. Why did the English build them like that?
   Because the first rail lines were built by the same people who built the pre-railroad tramways, and that’s the gauge they used.
7. Daddy, I still don’t understand. Why did ‘they’ use that gauge then?
   Because the people who built the tramways used the same jigs and tools that they had used for building wagons, which used that wheel spacing.
8. Why did the wagons have that particular odd wheel spacing?
   Well, if they tried to use any other spacing, the wagon wheels would break on some of the old, long distance roads in England, because that’s the spacing of the wheel ruts.
9. I understand. But why using this old rutted roads?
   Those roads have been used ever since the Imperial Rome built the first long distance roads in Europe (including England ) for their legions.
10. And why did the Roman built this wheel spacing?
    Roman war chariots formed the initial ruts, which everyone else had to match for fear of destroying their wagon wheels. Since the chariots were made for Imperial Rome, they were all alike in the matter of wheel spacing. Therefore the United States standard railroad gauge of 4 feet, 8.5 inches is derived from the original specifications for an Imperial Roman war chariot. Bureaucracies live forever.
11. Interesting story, I understand, that the maximum diameter of this modern rocket boosters is inherited from the wheel spacing of very old Imperial Rome war chariots. But why did the Romans decide for this wheel spacing?
    Well, to be honest. Imperial Roman army chariots were made just wide enough to accommodate the rear ends of two war horses. (Two horses’ asses.)

So, a major Space Shuttle design feature of what is one the world’s most sophisticated transportation system was determined over two thousand years ago by the width of a horse’s ass. And you thought being a horse’s ass wasn’t important?

If you liked that, you’ll probably like these too:

• Lean SG&A: Designing a service system that optimally responds to customer demand
• Danaher Business System – Implementing “real lean thinking”
• Great Video on two bin system within Hospitals
• Good books of my colleagues Chris and George
• supply chains (networks) compete, not companies