Title: DMAIC approach to using confidence intervals to assess conformance and reduce variation in net weight for a manufactured product: a case study

Authors: Kesiena Ezewu; Stephen O. Emumena; Monday E. Amagre

Addresses: Department of Mechanical Engineering, Delta State University, Abraka, Nigeria ' Department of Mechanical Engineering, Delta State University, Abraka, Nigeria ' Department of Mechanical Engineering, Delta State University, Abraka, Nigeria

Abstract: Markets have become global, and economic conditions are becoming more competitive. To ensure products meet international standards, manufacturers must begin to key into the average quantity system for products released into the market. This paper demonstrates the applicability of deploying confidence intervals within a DMAIC structure to assess conformance in the net weight of a manufactured product. We applied the I-MR chart to investigate stability in the manufacturing process and used the Ishikawa fishbone diagram to improve consistency in net weight, reducing the variability from a standard deviation of 1.5 to 0.39. The percentage out of specification improved from 76.6% to 0.02%. The process capability indices C_p and C_pk improved from 0.2 to 1.32 and -0.21 to 1.25, respectively. Finally, a 97.5% confidence interval affirmed the suitability of lots for the international market in view of AQS standards as demanded by the government and international regulatory agencies.

Keywords: DMAIC; product net weight; Six Sigma; confidence intervals; process capability.

DOI: 10.1504/IJSSCA.2024.139597

International Journal of Six Sigma and Competitive Advantage, 2024 Vol.15 No.1, pp.1 - 18

Received: 22 Nov 2022
Accepted: 17 Aug 2023
Published online: 04 Jul 2024 *

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