science

Issue tree

Issue tree is a science topic covered in the lgStudy science library. This page brings together a partial reference excerpt, illustrations, worked examples, real-world applications and a short study plan, so you can understand Issue tree rather than just read about it. In short: An issue tree, also called logic tree, is 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 identify its potential solutions.

Key takeaways

Issue tree belongs to science; place it in that map before memorising details.
Learn the definition first, then one example that makes the definition concrete.
Connect Issue tree to a quantity you can measure, compute or draw — that is where exam questions come from.
Reproduce the core statement of Issue tree from memory before moving on to harder problems.

Reference excerpt

An issue tree, also called logic tree, is 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 identify its potential solutions. They also provide a reference point to see how each piece fits into the whole picture of a problem.

Types According to professor of strategy Arnaud Chevallier, elaborating an approach used at McKinsey & Company, there are two types of issue trees: diagnostic ones and solution ones. Diagnostic trees break down a "why" key question, identifying all the possible root causes for the problem. Solution trees break down a "how" key question, identifying all the possible alternatives to fix the problem.

Rules Four basic rules can help ensure that issue trees are optimal, according to Chevallier:

Consistently answer a "why" or a "how" question Progress from the key question to the analysis as it moves to the right Have branches that are mutually exclusive and collectively exhaustive (MECE) Use an insightful breakdown The requirement for issue trees to be collectively exhaustive implies that divergent thinking is a critical skill.

Applications

In management interviews Issue trees are used to answer questions in case interviews for management consulting positions. A quantitative type of question, the market sizing question, requires the interviewee to estimate the size of a data group such as a specific segment of a population, an amount of objects, a company's revenues, or similar. The candidates are expected to use a structured and logical method of arriving at their answer, and using an issue tree provides a diagram to aid the candidate's logical reasoning. Issue trees are used for other types of case interview questions as well.

See also Fault tree analysis Five whys Horizon scanning Ishikawa diagram Root cause analysis Why–because analysis

References

Further reading Chevallier, Arnaud (11 April 2011). "Don't get lost in the terminology". powerful-problem-solving.com. Retrieved 2018-10-06. Issue trees, issue maps, logic trees, how trees, why trees, diagnostic trees, solution trees, decision trees, fact trees, hypothesis trees... How should you call your trees?... Call your tree what you want it to do. Chevallier, Arnaud (19 February 2011). "Use your issue tree as a decision tree". powerful-problem-solving.com. Retrieved 2018-10-06. Conn, Charles; McLean, Robert (2019). Bulletproof problem solving: the one skill that changes everything. Hoboken, NJ: John Wiley & Sons. ISBN 9781119553021. OCLC 1047803356. Friga, Paul N. (2009). "Develop the issue tree". The McKinsey engagement: a powerful toolkit for more efficient & effective team problem solving. McKinsey trilogy. Vol. 3. New York: McGraw-Hill. pp. 91–96. ISBN 978-0071497411. OCLC 166390293. Garrette, Bernard; Phelps, Corey; Sibony, Olivier (2018). Cracked it!: how to solve big problems and sell solutions like top strategy consultants. Cham: Palgrave Macmillan. doi:10.1007/978-3-319-89375-4. ISBN 9783319893747. OCLC 1028620732. Issue Trees and Hypothesis Trees - an Introduction

Illustrations

Worked examples

Example 1 — a first encounter with Issue tree

Start with the simplest possible case. Write down what Issue tree claims or describes in one sentence, then invent the smallest concrete situation in which that sentence is true. In science, the smallest case is usually a single object, a single equation or a single measurement. Check that every symbol or term in your sentence has a meaning in that case.

Example 2 — changing one variable

Take the situation from Example 1 and change exactly one quantity: double it, halve it, or set it to zero. Predict what should happen to Issue tree before you calculate. Comparing your prediction with the result is the fastest way to find out whether you understand the idea or only the words.

Example 3 — an exam-style question

Typical questions about Issue tree ask you to (a) state it precisely, (b) apply it to given data, and (c) explain a limitation. Practise writing all three answers in under five minutes; the third part is what separates a full-mark answer from an average one.

Applications of Issue tree

In research: Issue tree appears in science research whenever the underlying quantities have to be modelled precisely. Papers usually cite it as a starting assumption and then explore where it breaks down.
In technology and industry: Engineering practice reuses Issue tree in design rules, simulations and safety margins. Knowing the idea lets you read a specification sheet and understand why the numbers look the way they do.
In the classroom: Issue tree is common in secondary-school and first-year university syllabi. It links to neighbouring topics Diagrams, Futures techniques, Knowledge representation, so understanding it makes those chapters shorter.
In everyday life: Look for Issue tree outside the textbook — in sport, cooking, traffic, electronics or the sky above you. An example you found yourself is remembered far longer than one you were given.

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How to study Issue tree in 20 minutes

Read the reference excerpt below once, without taking notes.
Close the page and write down what Issue tree means in your own words.
Compare your version with the excerpt and mark what you missed.
Work through the three examples above with pen and paper.
Explain Issue tree out loud to somebody else — or to Teacher Smith in the lgStudy chat.

Frequently asked questions

What is Issue tree in simple terms?

Why does Issue tree matter?

Because it connects several science ideas at once: it gives you a definition you can apply, a quantity you can calculate, and a way to check whether a result is plausible.

How should I study Issue tree?

Read the excerpt, restate it from memory, then work through the examples and applications listed on this page. The five-step study plan above takes about twenty minutes.

What does this page cover?

It gives you a compact reference excerpt plus original lgStudy explanations, examples, applications and study material on Issue tree.