Regarding control charts, changing from three-sigma limits to two-sigma limits:
A) increases the probability of concluding nothing has changed, when in fact it has.
B) increases the probability of searching for an assignable cause when none exists.
C) decreases the probability that the process average will change.
D) decreases the probability that defects will be generated by the process.

Question

Quizplus · Accepted Answer

Changing from three-sigma limits to two-sigma limits on control charts makes the control limits tighter. This increases the likelihood of identifying a point outside the limits (indicating a potential issue) even when the process is operating normally, thus increasing the probability of searching for an assignable cause when none exists.

Regarding Control Charts, Changing from Three-Sigma Limits to Two-Sigma Limits