Cause-and-effect diagram

Learning objectives

• Build a cause-and-effect diagram for a garment defect.
• Use the 6M categories to avoid single-cause thinking.
• Turn candidate causes into hypotheses the Measure data can test.

One effect, many candidate causes

A cause-and-effect (fishbone) diagram records every plausible cause of one specific defect. The defect statement sits at the head of the fish and the bones carry categories such as Man, Machine, Method, Material, Measurement and Mother Nature.

The tool does not prove causes. Its job is to widen the search so the team stops jumping to the first plausible answer.

Working the diagram

• State the defect precisely: not “shade problem” but “shade band failure in denim wash lot 34.”
• Ask “why could this happen?” until each bone has at least three candidates.
• Circle causes the team believes are most likely; those become hypotheses.

Garment-factory example

A team investigates skipped stitches on a jersey polo shoulder seam. Under Machine they list needle bent, incorrect throat plate, timing off. Under Material they list yarn twist variation and low sewability. Under Method they list high back-tack tension and operator pulling fabric. Only three of the twelve candidates survive when the Measure data are checked.

Method

1. Write the defect clearly at the head of the fish.
2. Fill each 6M category with at least three specific causes.
3. Mark causes that the team believes are likely and testable.
4. Move likely causes into a Cause-and-Effect matrix or FMEA for scoring.

Common mistakes

• Using vague defect statements such as “quality problem.”
• Stopping at the first cause anyone mentions.