Sigma Level & Sigma Capability

Let me explain all the terms in sequence to understand better

What is sigma?

• Its a measure of smaller the better
• A measure that is used to quantify amount of variation in the process

What is sigma level?

• Its a measure of Larger the better
• A metric used to measure the performance of the process
• Sigma Level = No of sigma between LSL & Mean, No of sigma between USL & Mean
• Z = (USL-Xbar)/sigma; Z = (Xbar-LSL)/sigma
• Minimum value of above two is taken.
• It also called Z score
• Relation between sigma level and Sigma Capability is
• Capability = Z score/3