Table of Contents
Why Is the Six Sigma Goal of 3.4 DPMO Considered So Aggressive?
Understand why the Six Sigma quality standard of 3.4 defects per million opportunities (DPMO) is an aggressive goal for process improvement. This explanation covers the concept of near-perfect performance and the critical role of the 1.5 sigma shift, providing essential knowledge for your certification exam.
Question
Why is Six Sigma considered an aggressive goal?
A. Because it aims for only 3.4 defects per million opportunities
B. Because it guarantees zero variation
C. Because it applies only to manufacturing
D. Because it ensures 10% defect rate
Answer
A. Because it aims for only 3.4 defects per million opportunities
Explanation
This represents near-perfect performance. This target is considered exceptionally aggressive because it equates to a process that is 99.99966% defect-free, a level described as near-perfect performance.
The Standard of Near-Perfection
The core objective of Six Sigma is to reduce process variation and eliminate defects. A process operating at a Six Sigma level allows for only 3.4 defects for every one million opportunities (DPMO). This extremely low defect rate is far beyond typical quality levels and requires a highly disciplined, data-driven effort to achieve. For context, a process operating at a three-sigma level would produce 66,810 DPMO, which illustrates how demanding the Six Sigma standard is in comparison. The goal is to make processes so capable and consistent that the output is correct virtually all of the time.
The Role of the 1.5 Sigma Shift
The figure of 3.4 DPMO is derived from a statistical model that accounts for the natural tendency of a process to shift over the long term. A true six-sigma process, from a purely statistical standpoint, would only produce about two defects per billion opportunities. However, Six Sigma’s founders recognized that process means can drift from the target over time. They incorporated an empirical 1.5 sigma shift into the calculation to account for this long-term variation. This means that a process must be capable enough to perform at a six-sigma level, so that even if its center drifts by as much as 1.5 sigma, it will still yield no more than 3.4 defects per million opportunities. This built-in allowance for real-world process behavior is what makes the goal both pragmatic and highly aggressive.
Analysis of Incorrect Options
B. Because it guarantees zero variation: This is incorrect. Six Sigma aims to systematically reduce variation to a minimum, but it does not and cannot guarantee its complete elimination, as some natural variation exists in every process.
C. Because it applies only to manufacturing: This is false. While Six Sigma originated at Motorola in a manufacturing context, its principles and methods have been successfully applied across countless industries, including healthcare, finance, IT, and customer service.
D. Because it ensures 10% defect rate: This is incorrect and represents a very low-quality level. A 10% defect rate is equivalent to 100,000 DPMO, which is thousands of times higher than the Six Sigma standard.
Lean Six Sigma: Define, Analyze & Improve certification exam assessment practice question and answer (Q&A) dump including multiple choice questions (MCQ) and objective type questions, with detail explanation and reference available free, helpful to pass the Lean Six Sigma: Define, Analyze & Improve exam and earn Lean Six Sigma: Define, Analyze & Improve certificate.