Which methodology emphasizes reducing variation in business processes?

The methodology that emphasizes reducing variation in business processes is Six Sigma. This approach aims to improve process quality by identifying and removing the causes of defects and minimizing variability in manufacturing and business processes. It uses a data-driven methodology that relies on statistical tools and techniques to achieve improvements, focusing on producing consistent and predictable outcomes.

At the core of Six Sigma is the concept of standard deviation, where the goal is to keep processes within six standard deviations from the mean, thereby resulting in a high level of quality assurance and reliability. This systematic approach enables organizations to enhance performance and efficiency significantly.

While Lean focuses on waste reduction and improving process flow, and Agile is oriented towards flexibility and responding to change, these methodologies do not primarily concentrate on variation reduction as Six Sigma does. Similarly, Waterfall is a linear project management approach that is not fundamentally designed to measure or reduce variation in processes. Six Sigma's distinct focus on reducing variability makes it the correct choice for this question.