​Arrange the following steps of Six Sigma process in sequence.

A. Discover variation relationship for vital variables
B. Validate measurement systems, methods, and procedures
C. Validate repeatability, control systems, and implement SPC
D. Select critical-to-quality characteristics
E. Define performance limits and sources of variation​​

Choose the correct answer:

Correct option is D

The Six Sigma process follows a structured, data-driven methodology to improve quality by eliminating defects and minimizing variability. The correct sequence based on the DMAIC framework (Define, Measure, Analyze, Improve, Control) and internal logic of problem-solving is:

1. D. Select Critical-to-Quality (CTQ) Characteristics

   • This is part of the Define phase where customer requirements are translated into measurable quality attributes known as CTQs.

2. B. Validate Measurement Systems, Methods, and Procedures

   • In the Measure phase, it is essential to ensure the reliability of data collection systems by validating tools, methods, and instruments. Poor measurement leads to poor analysis.

3. E. Define Performance Limits and Sources of Variation

   • Still within the Measure/Analyze phase, you determine how the process behaves, what the natural performance limits are, and identify initial sources of variability.

4. A. Discover Variation Relationship for Vital Variables

   • Part of the Analyze phase, where statistical tools like regression and hypothesis testing are used to understand how input variables impact process variation and output quality.

5. C. Validate Repeatability, Control Systems, and Implement SPC (Statistical Process Control)

   • This belongs to the Control phase, where systems are stabilized and monitored for long-term consistency, and SPC tools are introduced to sustain improvements.

Thus, the correct and logical sequence is:
D → B → E → A → C

Information Booster:

• Six Sigma targets a defect rate of 3.4 per million opportunities, emphasizing precision and consistency.

• Measurement system analysis (MSA) ensures measurement tools are accurate and repeatable before analysis begins.

• SPC (Statistical Process Control) involves control charts to monitor process behavior and detect special cause variation.