Control Charts - Rule of Seven
6 years 8 months ago #1317
I am confused about the "out of control" process indication on a control chart. According to my knowledge, a process is out of control if:
-A data point falls outside of the upper or lower control limits.
-7 data points in a row fall above or below the mean.
-7 data points in a row trending up or down (crossing the mean).
The PMBOK Guide (8.2.3 page 196) states that "a process is considered out of control when a data point exceeds a control limit or if seven consecutive points are above or below the mean". I listened PrepCast 08.04 and it also said that "Seven times fall onto the same side of the mean-->Investigate".
As I understood from the language in the PMBOK Guide and the PrepCast, if out of 7 consecutive data points, 4 fall under and 3 fall above the mean, the process should not be counted as out of control.
I surely will take whatever PMBOK Guide says but I wanted to verify first.
Thanks so much,
Last Edit: 6 years 8 months ago by Orkun Toros. Reason: Corrected sentence
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