Lean Six Sigma Green Belt Certification Lean Six Sigma Green Belt DMAIC: Measure Phase Tools 1

Question 1

What is the key difference between the Cp and Cpk process capability indices?

Accepted Answer

Cpk accounts for process centering while Cp measures only spread relative to specification width

Answer

Cpk incorporates where the process mean sits relative to the specification limits, penalizing processes that are off-center. Cp only compares the process spread to the specification width, ignoring whether the process is centered — so two processes with identical Cp values can have very different Cpk values.

Question 2

In Measurement System Analysis (MSA), what does 'reproducibility' specifically quantify?

Accepted Answer

Variation in measurements when different operators measure the same part with the same instrument

Answer

Reproducibility captures operator-to-operator variation — how much measurements differ when different appraisers measure the same part using the same gauge. Repeatability, by contrast, is the variation seen when one operator repeatedly measures the same part.

Question 3

A process operating at Six Sigma quality level produces how many defects per million opportunities (DPMO)?

Accepted Answer

3.4 DPMO

Answer

A Six Sigma process produces no more than 3.4 DPMO. This figure accounts for a 1.5-sigma long-term shift in the process mean that is assumed to occur in real-world processes, making 3.4 DPMO the accepted benchmark for Six Sigma performance.

Question 4

Which control chart is most appropriate for monitoring the mean of a continuous variable when measurements are collected in subgroups of n = 5?

Accepted Answer

X-bar and R chart

Answer

The X-bar and R chart is designed for continuous (variable) data collected in rational subgroups, plotting subgroup means on the X-bar chart and subgroup ranges on the R chart. The p-chart, c-chart, and u-chart are all designed for attribute (count or proportion) data.

Question 5

A four-step process has first-time yields of 95%, 92%, 88%, and 90% respectively. What is the Rolled Throughput Yield (RTY)?

Accepted Answer

69.2%

Answer

RTY is calculated by multiplying the first-time yield of each step: 0.95 × 0.92 × 0.88 × 0.90 = 0.6919, approximately 69.2%. RTY exposes hidden rework and scrap that a final-step yield metric alone would conceal, making it a critical Measure phase metric.

Lean Six Sigma Green Belt Certification Practice Test

Lean Six Sigma Green Belt Certification Practice Test

Lean Six Sigma Green Belt Certification Lean Six Sigma Green Belt DMAIC: Measure Phase Tools 1