Biochemia Medica, Vol. 30 No. 1, 2020.
Short communication, Note
https://doi.org/10.11613/BM.2020.010901
Six Sigma revisited: We need evidence to include a 1.5 SD shift in the extraanalytical phase of the total testing process
Abdurrahman Coskun
orcid.org/0000-0002-1273-0604
; Department of Medical Biochemistry, Acıbadem Mehmet Ali Aydınlar University, School of Medicine, Istanbul, Turkey
Cristiano Ialongo
; Department of Physiology and Pharmacology, Sapienza University of Rome, Rome, Italy
Abstract
The Six Sigma methodology has been widely implemented in industry, healthcare, and laboratory medicine since the mid-1980s. The performance
of a process is evaluated by the sigma metric (SM), and 6 sigma represents world class performance, which implies that only 3.4 or less defects (or
errors) per million opportunities (DPMO) are expected to occur. However, statistically, 6 sigma corresponds to 0.002 DPMO rather than 3.4 DPMO.
The reason for this difference is the introduction of a 1.5 standard deviation (SD) shift to account for the random variation of the process around its
target. In contrast, a 1.5 SD shift should be taken into account for normally distributed data, such as the analytical phase of the total testing process;
in practice, this shift has been included in all type of calculations related to SM including non-normally distributed data. This causes great deviation
of the SM from the actual level. To ensure that the SM value accurately reflects process performance, we concluded that a 1.5 SD shift should be used
where it is necessary and formally appropriate. Additionally, 1.5 SD shift should not be considered as a constant parameter automatically included in
all calculations related to SM.
Keywords
extraanalytical phase; shift; Sigma metric; Six Sigma; total testing process
Hrčak ID:
234151
URI
Publication date:
15.2.2020.
Visits: 887 *