What critical fact is Six Sigma built on?

Six Sigma is fundamentally focused on the concept of reducing variability within processes to improve quality and efficiency. The effectiveness of Six Sigma comes from its methodology, which aims to identify and eliminate defects, errors, and waste that arise from process variability. The underlying principle is that variability, whether in manufacturing, services, or logistics processes, leads to unpredictability and inconsistency in outcomes, which ultimately affects customer satisfaction and operational efficiency.

By using statistical tools and techniques, Six Sigma practitioners analyze process data to identify sources of variation. They then implement strategies to minimize this variability, leading to more reliable outputs and improved processes. The emphasis on controlling and reducing variability is what distinguishes Six Sigma as a powerful approach to process improvement in various industries, including international logistics.

In this context, the other options do not encapsulate the core belief of Six Sigma. While cash flow, capacity understanding, and human behaviors are relevant to broader business operations or decision-making, they do not address the foundational principle of variability being the source of defects in the Six Sigma framework.