The Five Whys is a simple but great
technique to use to
solve problems. It is a question-asking method used to explore
the cause/effect relationships underlying a particular
Ultimately, the goal of applying the 5 Whys method is
to determine a root cause of a defect or problem.
Problem Solving at Toyota
Taiichi Ohno, former
Toyota vice president,
once gave the following example of finding the real cause of a machine
Q1: Why did the machine stop?
A1: Because the fuse blew due to
Q2: Why there was an overload?
A2: Because the bearing
lubrication was inadequate.
Q3: Why was the lubrication
A3: Because the lubrication pump
was not functioning right.
Q4: Why wasn't the lubrication
pump working right?
A4: Because the pump axle was worn
Q5: Why was it worn out?
A5: Because sludge got in.