Certified Six Sigma Black Belt Exam FREE Certified Six Sigma Black Belt Statistical Process Control (SPC) Questions and Answers 3

Question 1

An I-MR chart shows the individual values chart in control, but the moving range chart has a point above the upper control limit. What should be investigated first?

Accepted Answer

Whether a single large jump occurred between two consecutive observations

Answer

Whether the process mean has shifted

Answer

Whether the subgroup size should be increased

Answer

Whether the specification limits need revision

Question 2

Which assumption is most critical for the valid interpretation of a standard X-bar and R control chart?

Accepted Answer

Observations within each subgroup must be independent

Answer

The data must follow a normal distribution exactly

Answer

The process capability index must exceed 1.0

Answer

Each subgroup must contain at least 10 observations

Question 3

A Six Sigma Black Belt notices 8 consecutive points on one side of the center line on an X-bar chart. The process is considered:

Accepted Answer

Out of control due to a run indicating a likely mean shift

Answer

In control because no points exceed the control limits

Answer

Capable but not stable

Answer

In need of tighter specification limits

Question 4

What is the Average Run Length (ARL) for a Shewhart control chart using only the 3-sigma rule when the process is in control?

Accepted Answer

370 subgroups

Answer

100 subgroups

Answer

270 subgroups

Answer

500 subgroups

Question 5

A CUSUM chart is preferred over a standard Shewhart chart in which situation?

Accepted Answer

When detecting small sustained shifts of 1.5 sigma or less

Answer

When detecting large sudden shifts in the process mean

Answer

When monitoring attribute data with variable sample sizes

Answer

When the data is highly non-normal

Question 6

When transforming non-normal data for use with standard SPC charts, which approach should be attempted first?

Accepted Answer

Apply a Box-Cox transformation to achieve approximate normality

Answer

Widen the control limits to accommodate the skewness

Answer

Use attribute charts instead of variables charts

Answer

Discard outliers until the data appears normal