Choose Lean, Six Sigma, or both for the problem in front of you.

Start with the gap, not a list of tools

Lean Six Sigma combines attention to flow with measurement of variation and defects. Describe one customer or production problem first. Long queues call for different checks from a dimension that drifts toward its tolerance limit.

Do not promise faster output from a local defect reduction until you understand the constraint and rework route. Use Lean versus Six Sigma for the broader method comparison.

Define and measure the same outcome

Define the unit, defect, process boundary and observation window. Check the measurement system before comparing operators or shifts. Retain reworked parts in the history without relabelling them as first-pass successes.

Use DMAIC to test an explanation

Define the problem and customer requirement. Measure a representative baseline. Analyze competing explanations with records, not a vote. Improve through an approved trial. Control by specifying the measurement, response and owner.

For the housing example, compare tool age, fixture condition and product mix before blaming a setting. A relationship in the records suggests a test; it does not authorize an automatic adjustment.

Evaluate the trial beyond the headline percentage

Compare matched operating exposure and product mix. Count scrap, rework time, inspection effort and downstream output as well as first-pass yield. Report sample size and remaining uncertainty.

A simulated improvement is a prediction. A short trial is early evidence. Keep each separate from a verified sustained result, and check safety and quality consequences before adoption.

Write the response that keeps the change working

Document the approved setup, sampling rule, escalation and owner. Use control charts when their assumptions fit; an arbitrary target line is not a statistical limit.

Review the control after tooling, material or routing changes. If the original problem returns, preserve the evidence and reopen the investigation rather than silently changing the baseline.

1. Record

   Keep the baseline and observation window.

2. Review

   Compare the result with the prediction and check side effects.

3. Assign

   Name the next action owner and review date.

What does “Six Sigma efficiency” measure?

The phrase does not identify one standard operating percentage. Six Sigma describes an approach to variation and defects; it does not supply the numerator and denominator of every efficiency calculation.

If the question concerns waiting, define a cycle-efficiency time share with its process boundary. If it concerns units passing without repair, use first-pass yield for a stated cohort. Capability indices examine a suitable process distribution against specifications and are not interchangeable with either measure. Choose the customer question first, then name the calculation and its assumptions.