Issue tree

Issue tree

Wikipedia describes an Issue tree as a graphical breakdown of a question that dissects it into its different components vertically, and that progresses into details as it reads to the right.

Issue trees are useful in problem-solving to identify the root causes of a problem as well as to find potential solutions.

--> Heuristic tools 

There are two types of issue trees: diagnostic and solution.
ExploreReflect  Diagnostic trees breakdown a “Why” key question, identifying all the possible causes for the problem. “Why” issue tree is more powerful tool than famous 5 Whys approach because it doesn’t isolate a single root cause but can consider several sources of the problem.

CreateReflect  Solution tree breakdowns a “How” key question, identifying all the possible alternatives to fix the problem.

An issue tree needs following some basic rules:

  • Progress from the key question to the analysis. (Chevallier., 2010)
    – A tree goes from the key question to the data sources.
    – Each tree follows the same pattern – either it is a “how” or a “why” but not both.
    – “How” trees do not describe a sequential process but show alternative solutions.
    – Items in the tree have to be clear questions, action verbs or hypotheses. Not just titles that have to be additionally clarified.
    – Each move to the right must bring some value.
    – Each item has at least 2 sub-items. If there is only 1 sub-item either there are other possibilities or some sub-items are redundant.
"Why" issue tree
Example of “why” Issue tree for the problem with temperature in the server room, made in MindJet
"How" issue tree
Example of “how” Issue tree for the problem with temperature in the server room (green are possible options), made in Excel
  • Be ICE
    – Independent and Collectively Exhaustive (ICE) means that all items are independent of each other and at least one of them must occur. “For example, when rolling a six-sided die, the outcomes 1, 2, 3, 4, 5, and 6 are Collectively Exhaustive, because they encompass the entire range of possible outcomes.”

    Issue tree is Sequencing,
    Evidencing, and Holistic.

    – McKinsey recommends relying on Mutually Exclusive and Collectively Exhaustive groupings for an issue tree creation. However, in practice, Mutually Exclusive requirement is not efficient because of a combination of different approaches can give much better results than just one exclusive solution. So in the real life problem-solving ICE approach is mostly exploited. (Chevallier)

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