Question: Consider the control charts below. For each state if you think the process is in control or if there is reason to suspect that either the mean has shifted, the variance has shifted, or both have shifted.

a.

Solution: The process is in control; it doesn’t seem that neither the mean nor the variance have shifted.

b.

Solution: The process is in control; it doesn’t seem that neither the mean nor the variance have shifted (Even though there are a little too many points above the centerline, which could be an indication of an unusual cause)

c.