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» 1.5 시그마 시프트

1.5 시그마 시프트

1990
  • Mikel Harry
제조 분야의 공정 역량 메트릭을 분석하는 품질 관리 엔지니어.

(설명을 위한 생성된 이미지입니다)

The 1.5 sigma shift is an empirical correction used in 식스 시그마 calculations to account for the long-term dynamic variation of a process. It posits that over time, a process mean will tend to drift by about 1.5 standard deviations from its short-term centered position. This shift is the reason a 6 sigma process corresponds to 3.4 DPMO, not the theoretical 2 defects per billion.

Disclaimer: the 1.5 sigma shift is one of the most debated aspects of Six Sigma. It originates from the observation that short-term data, collected over a brief period, typically shows less variation than long-term data from the same process. This is because over longer periods, factors like tool wear, material variations, operator differences, and environmental changes cause the process mean to drift. The 1.5 sigma value was determined empirically by Motorola engineers as a reasonable general estimate for this drift. By incorporating this shift, Six Sigma provides a more realistic, long-term view of process performance. The calculation for DPMO is thus based on the probability of an outcome falling outside a specification limit that is [latex]4.5\sigma[/latex] from the drifted mean ([latex]6\sigma – 1.5\sigma[/latex]). Critics argue that the 1.5 value is arbitrary and that a well-controlled process should not drift this much. Proponents argue it’s a pragmatic adjustment that makes the Six Sigma standard more applicable to real-world industrial processes.

UNESCO Nomenclature: 3308
산업공학 및 기술

유형

추상 시스템

분열

점진적

용법

널리 사용됨

전구체

  • Walter A. Shewhart’s work on common and special cause variation
  • long-term vs. short-term process capability studies
  • empirical observations of industrial processes
  • control chart theory

응용 프로그램

  • calculating long-term process capability (Cpk, Ppk)
  • setting realistic quality targets in manufacturing
  • risk assessment in financial modeling
  • reliability engineering for long-life products

특허:

NA

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Related to: 1.5 sigma shift, process drift, six sigma, dpmo, statistical process control, process capability, long-term variation, motorola, quality control, standard deviation.

역사적 맥락

1.5 시그마 시프트

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