five Whys

5why TPS dictionary

five Whys


The 5 why’s typically refers to the practice of asking, five times, why the failure has occurred in order to get to the root cause/causes of the problem. There can be more than one cause to a problem as well. In an organizational context, generally root cause analysis is carried out by a team of persons related to the problem. No special technique is required.

An example is in order:

1.Why did the machine stop? Because There was an overload and the fuse blew.

2.Why was there an overload? Because the bearing was not sufficiently lubricated.

3.Why was it not lubricated? Because the lubrication pump was not pumping sufficiently.

4.Why was it not pumping sufficiently?Because the shaft of the pump was worn and rattling.

5.Why was the shaft wirn out? Because There was no strainer attached and metal scraps got in.