Module 1 · Lesson 9 of 14
Basic process thinking and Y = f(X)
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Learning objectives
- Identify Y and candidate Xs for a garment process.
- Distinguish input, in-process and output measures.
- Avoid treating correlation as proof of cause.
Y = f(X) as a thinking model
The equation is a thinking model, not proof. Teams define the outcome Y, generate plausible input factors Xs, collect reliable data and validate which inputs materially change the output.
Garment-factory example
Seam strength (Y) may depend on thread, needle, stitch density, seam type, fabric construction, tension and operator method. Only some of these prove to be vital Xs after testing.
Method
- Define Y operationally with units.
- Map the process and list Xs.
- Prioritize Xs by knowledge and risk.
- Test relationships and control confirmed vital Xs.
Common mistakes
- Measuring many variables without a question.
- Controlling unverified causes.
Knowledge check
Pick one answer per question. Explanations appear after you submit.
1. When does a candidate X become a root cause?
2. Output inspection controls:
Author: NOSK.life · Last reviewed: 2026-07-21