Fishbone Diagram

Fish bone diagram (aka. Ishikawa and cause-and-effect) is a structured brainstorming technique to identify potential underlying factors or causes of a problem and them into useful categories.
The problem is represented at the head or mouth of the fish and the bones represent different categories of causes, each with a list of possible contributory causes. Team can use the “5 Whys Technique” or keep asking “why” questions to find deeper causes and organize them into relevant categories.

Typically used categories of a fishbone diagram include materials, measurements, people, time, energy, machinery/infrastructure, and environment.