Upper and lower boundaries of the “desired” values of y are plotted as lines. These are the _________ and _________ The average value (X, said as “X-bar”) is centred b/w the control limits. The range of the control limits, R, depends on the statistical variation of the process.

• A. Higher limit and lower limit
• B. Upper control limit and lower control limit
• C. Max. limit and Min. Limit
• D. Upper point and lower point