Certified Six Sigma Black Belt Exam Certified Six Sigma Black Belt Statistical Process Control (SPC) Questions and Answers 2

Question 1

A Six Sigma Black Belt notices that all plotted points on an X-bar chart fall within the control limits but seven consecutive points are above the center line. What should be concluded?

Accepted Answer

A special cause of variation is likely present

Answer

The process is in statistical control

Answer

The control limits need to be recalculated

Answer

The sample size is too small

Question 2

Which control chart is most appropriate for monitoring the number of paint defects found on each automobile body when the inspection area varies from vehicle to vehicle?

Accepted Answer

u chart

Answer

c chart

Answer

p chart

Answer

np chart

Question 3

When calculating the process capability index Cpk, a Black Belt obtains Cpk = 1.0 and Cp = 1.5. What does this indicate about the process?

Accepted Answer

The process is capable but not centered within the specification limits

Answer

The process is perfectly centered between the specification limits

Answer

The process spread is too wide for the specifications

Answer

The specification limits need to be widened

Question 4

An EWMA chart is preferred over a Shewhart X-bar chart in which of the following situations?

Accepted Answer

When detecting small sustained shifts in the process mean

Answer

When detecting large shifts in the process mean

Answer

When the subgroup size is greater than 10

Answer

When monitoring attribute data

Question 5

A process has a Pp of 1.33 but a Cp of 0.89. What is the most likely explanation?

Accepted Answer

The process has significant between-subgroup variation that inflates overall variability

Answer

The process has excessive within-subgroup variation

Answer

The long-term performance is better than the short-term capability

Answer

The between-subgroup variation is smaller than the within-subgroup variation

Question 6

On a moving range (MR) chart used with an individuals (I) chart, what is the upper control limit formula when d2 = 1.128 and D4 = 3.267?

Accepted Answer

UCL = D4 × R-bar

Answer

UCL = 3 × MR-bar / d2

Answer

UCL = MR-bar + 3 × d2

Answer

UCL = D4 × MR-bar / d2

A Six Sigma Black Belt notices that all plotted points on an X-bar chart fall within the control limits but seven consecutive points are above the center line.What should be concluded?

A Six Sigma Black Belt notices that all plotted points on an X-bar chart fall within the control limits but seven consecutive points are above the center line.
What should be concluded?