There seems to be some confusion&#x2F;mis-interpretation about the 5 part.<p>This is called 五回のなぜ in Japanese (&quot;Go-kai no naze,&quot; or Why Five Times) and refers to root cause analysis. Of course the number of times the process need be repeated until the root cause is identified is variable. Five in this case is merely a jingly mnemonic, as Japanese people are so fond of.