A quality engineer at a canning company assesses whether the can-filling process is in control. Each hour, the engineer collects a subgroup of 10 cans. To minimize the within-subgroup (can-to-can) variation, the engineer collects the cans for a given subgroup in a short period of time.
The quality engineer creates an Xbar chart to monitor the weight of the cans.
One point is out-of-control on the Xbar chart. The engineer concludes that the process is not stable and should be improved.