Lean Six Sigma Black Belt Certification Statistical Process Control (SPC) 3

Question 1

Which control chart is most appropriate for monitoring the number of defects per unit when the subgroup size varies?

Accepted Answer

u-chart

Answer

The u-chart monitors defects per unit and accommodates variable subgroup sizes, unlike the c-chart which requires a constant area of opportunity.

Question 2

Process capability ratio Cp differs from Cpk in that Cp:

Accepted Answer

Ignores process centering while Cpk accounts for it

Answer

Cp measures only the spread relative to specifications without regard to centering, while Cpk adjusts for how far the process mean is from the nearest specification limit.

Question 3

An EWMA chart uses a smoothing parameter λ (lambda). What happens when λ approaches 1?

Accepted Answer

The chart behaves more like a Shewhart individuals chart

Answer

As λ approaches 1, the EWMA chart places nearly all weight on the most recent observation, approximating a Shewhart individuals (I) chart.

Question 4

Which situation would make a P-chart inappropriate?

Accepted Answer

When defects per unit are being tracked

Answer

The P-chart monitors the proportion of nonconforming items (pass/fail), not the count of defects per unit; for defects per unit, a u-chart or c-chart should be used.

Question 5

In a Gage R&R study, which component of variation confirms that the measurement system discriminates between parts?

Accepted Answer

Part-to-part variation

Answer

Part-to-part variation being large relative to measurement system variation confirms the gage can distinguish between different parts, indicating adequate discrimination.

Lean Six Sigma Black Belt Certification Practice Test

Lean Six Sigma Black Belt Certification Practice Test

Lean Six Sigma Black Belt Certification Statistical Process Control (SPC) 3