The higher the sigma level of a process the better the performance.

The sigma level is a key metric in Six Sigma that quantifies process capability. It measures how many process standard deviations fit within the customer's upper and lower specification limits. A higher sigma level indicates that the process variation is small compared to the allowed specification width. This translates directly to a lower probability of producing a defect. For example, a process operating at a 6-sigma level produces only 3.4 defects per million opportunities (DPMO), which is considered world-class performance. Conversely, a lower sigma level implies more defects and poorer performance.

B. False: This is incorrect. A lower sigma level signifies that the process has more variation relative to customer specifications, leading to a higher defect rate and, consequently, poorer performance.

1. Montgomery, D. C. (2013). Introduction to Statistical Quality Control (7th ed.). Wiley. In Chapter 9, Section 9.7, "Six-Sigma Process Capability," it is explained that the objective of a Six Sigma program is to improve processes so that the sigma level increases, which corresponds to a reduction in defects and improved performance.

2. Antony, J., & Banuelas, R. (2002). Key ingredients for the effective implementation of Six Sigma program. Measuring Business Excellence, 6(4), 20-27. On page 21, the authors state, "The sigma is a metric that indicates how well a process is performing. The higher the sigma value, the better the process is performing." DOI: https://doi.org/10.1108/13683040210451679

3. Pyzdek, T., & Keller, P. A. (2018). The Six Sigma Handbook (5th ed.). McGraw-Hill Education. Chapter 7, "Measuring Process Performance," provides a table (Table 7.1) that explicitly shows the inverse relationship between Defects Per Million Opportunities (DPMO) and the sigma level, demonstrating that as sigma level increases from 2 to 6, DPMO decreases dramatically, indicating better performance.