In a hypothetical situation, if all within time, piece to piece, and measurement variation were removed from a process, what would be left?

Question

Options

• ANothing it would all be eliminated
• BInherent process variation
• CProduct spread
• DTime to time variation

• A
  5% (2)
• B
  86% (37)
• C
  2% (1)
• D
  7% (3)

Explanation

Option B is correct because inherent process variation is the irreducible "common cause" noise built into the process itself - it remains after all identifiable external sources of variation are stripped away. Think of it as the process's baseline fingerprint: no matter how perfectly you control time, parts, and measurement tools, some fundamental variation always persists.

Why the distractors are wrong:

• A (Nothing): Incorrect because real-world processes always retain some baseline variation; zero variation is physically impossible.
• C (Product spread): This describes the spread of output values - it's a symptom of variation sources, not a standalone type that persists independently. Removing the listed sources reduces product spread; it doesn't leave product spread behind.
• D (Time to time variation): This is one of the sources being removed in the question, so it cannot be what's left over.

Memory tip: Use the acronym WIMP - Within-time, Inherent, Measurement, Piece-to-piece. Remove W, M, and P from any process and Inherent variation is always the survivor. Inherent = irreducible.

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