A X-bar control chart has an upper control limit of 0.65 inch and a lower control limit of 0.35 inch. The results of the next six samples are 0.60, 0.37, 0.45, 0.48, 0.53, and 0.62 inches. What should you do?
Nothing, the process is in control
Investigate because three observations are above the mean.
Investigate because there is a run.
Investigate because there is a trend.
increase the sample size.

Which of the four X-bar control charts illustrated below should prompt an investigation of the process being monitored?
Only A calls for an investigation
All of the above (A,B,C, and D)
A, B, C only call for an investigation.
All charts are acceptable (no investigation).
B, C, D only call for an investigation.