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Investigate Possible Causes: An Evidence Workbook

Lean Six Sigma, Quality & Process ImprovementWorkbooks

By Jefferson Otonbara Imgbi

Published
8 October 2026
Last reviewed
8 October 2026
Organise observations, possible explanations and follow-up questions. Avoid treating the first plausible cause as a proven conclusion.
Image
A magnifying glass over connected components beside evidence cards and a notebook.

Describe the condition first

Root-cause work should start with the problem being investigated. ASQ presents root cause analysis as a family of approaches for examining causes. This workbook is an introductory way to organise an investigation; it does not establish a cause by itself.

Use a fictional enquiry process where some requests wait for assignment. Record the condition and the period. Avoid starting with a judgement about a person or a preferred solution.

Generate more than one explanation

Discuss possible influences such as information quality, handover rules, system behaviour, workload or timing. Record them as hypotheses or questions. Include evidence that could challenge each explanation.

For the fictional process, one possibility is that incomplete enquiries cannot be assigned. Another is that the handover rule is unclear. These may coexist, or neither may explain the observed delay. The team needs to investigate.

Connect each explanation to evidence

State what observation or authorised record would help check the idea. Identify the source, responsible person and collection approach. Separate what is observed from what is inferred.

If delays appear near a handover, examine how work is transferred and whether other conditions change at the same time. An association is a reason to investigate rather than automatic proof of causation.

Review disagreement and uncertainty

Record alternative interpretations and missing information. Ask whether the proposed explanation fits the cases examined and what exceptions remain. Avoid forcing every event into one story.

A question such as why did this happen can help a conversation, but repeating it a fixed number of times does not prove a root cause. The workbook asks for supporting observations and a review of the reasoning.

Choose the next investigation

Agree which explanation has enough support for further action and which needs more work. Record the decision, owner and review point. Seek specialist support for technical or statistical questions outside the team’s competence.

Download the workbook and use fictional evidence. Ask a second reader to distinguish the facts, possible causes and next questions. Revise any statement that appears more certain than the evidence permits.

Source and practice note

ASQ provides the root cause analysis background. The workbook fields and fictional examples are original RDE material. The exercise and fictional examples are original RDE learning material.

ASQ root cause analysis overview

Cover image: AI-generated illustrative scene created specifically for this resource.

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Printable PDF and editable Word document. Version 2.0, 8 October 2026. Personal and internal organisational adaptation permitted with Jefferson Otonbara Imgbi author credit retained.

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