Necessary and Sufficient Conditions

Updated: 12/20/2016
Necessary and Sufficient Conditions
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Whys Biz Lesson Plans

What are the 5 Whys

By Nathanael Okhuysen

When something goes wrong, especially in a large organization, there can be an instinct to point fingers and shift blame. This probably isn’t the best way to prevent the problem from arising in the future though. Sakichi Toyoda, the founder of Toyota Motor Company, developed the “5 Whys” process, a type of root cause analysis, to identify and fix problems that arose within the company. It has since been widely adopted as part of lean manufacturing, Kaizen, and Six Sigma methodology.

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Storyboard Description

causation - cause and effect - Root Cause analysis

Storyboard Text

  • Neither Necessary, nor Sufficient
  • HELLO!
  • Sufficient, but not Necessary
  • Being human means you can talk. (Some birds can speak, and some humans cannot)
  • Necessary, but not Sufficient
  • Causation
  • The sidewalk is wet because it's raining. (The sidewalk could get wet from some other cause, a hose, for instance.)
  • Necessary and Sufficient
  • You have to be 30 years old to serve as a US Senator. (Being 30 is not enough to make you a senator though.)
  • Lighting causes thunder. (Thunder cannot be caused by anything other than lightning.)