Which Is a Rule of Thumb to Indicate an Out-Of-Control $\overline { x^ { * } }$

Multiple Choice

Which is a rule of thumb to indicate an out-of-control process on the $\overline { x^ { * } }$ chart?

A) Single point outside one sigma
B) Two of three successive points outside one sigma on the same side of the centerline
C) Four of five successive points on the same side of the centerline
D) Nine successive points alternating in sign