For a 3-Sigma X-Bar Chart Where the Process Standard Deviation

Multiple Choice

For a 3-sigma x-bar chart where the process standard deviation is known,the upper control limit:

A) is 3σ below the mean of sample means for a 3σ control chart.
B) is 3σ above the mean of sample means for a 3σ control chart.
C) is 3σ/ below the mean of sample means for a 3σ control chart.
D) is 3σ/ above the mean of sample means for a 3σ control chart.
E) cannot be calculated unless the average range is known.