Estimating the Process Sigma Level Based on Information from Statistical Process Control or Process Capability Analysis
DOI:
https://doi.org/10.12776/qip.v30i1.2335Keywords:
process sigma level, critical-to-quality characteristic, defect, defect opportunityAbstract
Purpose: The article proposes an approach to estimating the process sigma level based on information from statistical process control or process capability analysis.
Methodology/Approach: The z-score for each critical-to-quality characteristic and for the overall process is estimated from the data obtained in statistical process control or process capability analysis.
Findings: The proposed procedure for estimating the sigma level offers several advantages over the traditional method.
Research Limitation/Implication: We assume that each critical-to-quality characteristic is linked to only one type of defect opportunity, which can result in only one defect of that type on a single unit. We only consider continuous, normally distributed, and nominal critical-to-quality characteristics with two possible values: non-defective and defective.
Originality/Value of paper: The proposed procedure enables us to use information from statistical process control and process capability analysis to estimate the process sigma level and provides additional valuable insights into the process.
References
Benková, M., Bednárová, D., & Bogdanovská, G. (2024). Process capability evaluation using capability indices as a part of statistical process control. Mathematics, 12(11), 1679. https://doi.org/10.3390/math12111679
Chen, K.-S., Ouyang, L.-Y., Hsu, C.-H., & Wu, C.-C. (2009). The communion bridge to Six Sigma and process capability indices. Quality & Quantity, 43(3), 463–469.
Costa, A. R., Barbosa, C., Santos, G. M., & Alves, R. (2019). Six Sigma: Main metrics and R-based software for training purposes and practical industrial quality control. Quality Innovation Prosperity, 23(2), 1–18.
International Organization for Standardization. (2011). Quantitative methods in process improvement – Six Sigma – Part 1: DMAIC methodology (ISO Standard No. 13053-1). Geneva, Switzerland: ISO copyright office.
International Organization for Standardization. (2011). Quantitative methods in process improvement — Six Sigma — Part 2: Tools and techniques (ISO 13053 – 2:2011). Geneva, Switzerland: Author.
International Organization for Standardization. (2014). Statistics – Vocabulary and symbols Part 2: Applied statistics (ISO 3534 – 2:2014). Geneva, Switzerland: Author.
iSixSigma. (n.d.). Sigma to DPMO to Yield to C_pk Table: Take Control of Your Data. Retrieved from https://www.isixsigma.com/sigma-level/sigma-to-dpmo-to-yield-to-cpk-table.
Montgomery, D. C. (2020). Introduction to statistical quality control (8th ed.). Hoboken, NJ: John Wiley & Sons.
Six Sigma conversion table. (n.d.). Six Sigma conversion table. Retrieved from https: //www.moresteam.com/toolbox/six-sigma-conversion-table.
Stamatis, D. H. (2003). Six Sigma for financial professionals. Hoboken, NJ: John Wiley & Sons.
Terek, M. (2023). How to estimate the process sigma level. Quality Innovation Prosperity, 27(3), 1–15.
Terek, M., & Hrnčiarová, Ľ. (2004). Štatistické riadenie kvality. Bratislava, Slovakia: Iura Edition.
Tošenovský, J., & Tošenovský, F. (2019). Possibilities of using graphical and numerical tools in the exposition of process capability assessment techniques. Quality Innovation Prosperity, 23(2), 113–129.
Zgodavová, K., Bober, P., Majstorovič, V., Monková, K., Santos, G., & Juhászová, D. (2020). Innovative methods for small mixed batches production system improvement: The case of a bakery machine manufacturer. Sustainability, 12(15), 6266. https://doi.org/10.3390/su12156266
Downloads
Published
Issue
Section
License
Copyright (c) 2026 Milan Terek
This work is licensed under a Creative Commons Attribution 4.0 International License.
This is an open access journal which means that all content is freely available without charge to the user or his/her institution. Users are allowed to read, download, copy, distribute, print, search, or link to the full texts of the articles in this journal without asking prior permission from the publisher or the author. This is in accordance with the BOAI definition of open access. This journal is licensed under a Creative Commons Attribution 4.0 License - https://creativecommons.org/licenses/by/4.0.
Authors who publish with the Quality Innovation Prosperity agree to the following terms:
- Authors retain copyright and grant the journal right of first publication with the work simultaneously licensed under a Creative Commons Attribution License that allows others to share the work with an acknowledgement of the work's authorship and initial publication in this journal.
- Authors are able to enter into separate, additional contractual arrangements for the non-exclusive distribution of the journal's published version of the work (e.g., post it to an institutional repository or publish it in a book), with an acknowledgement of its initial publication in this journal.
- Authors are permitted and encouraged to post their work online (e.g., in institutional repositories or on their website) prior to and during the submission process, as it can lead to productive exchanges, as well as earlier and greater citation of published work.
