On a highly automated food processing line, a quality professional wants to chart the weight of packages. The recommended control chart is an X-bar – S chart and not the typical X-bar – R chart, in wide use throughout the facility. Which of the following is the most logical reason for this switch?

OPTIONS

• The X-bar control limits will be tighter
• The supervisor obviously wants some variety in control chart usage
• Only one control chart will be required
• The X-bar and S values will come automatically from a weight checker

The X-bar and S values will come automatically from a weight checker

Explanation:

This question requires familiarity with X-bar – S charting and automated process equipment. Option C is incorrect. Two charts will still be necessary. Option B is a filler option. Option A may or may not be correct. This answer is dependent upon the sample size. In either event, the plot points and control limits will be proportional (assuming a reasonably small sample size) and is not a logical reason for making the X-bar – S selection. The assumption must be that the supervisor knows that the X-bar – S values can be supplied from an automated weight checker. So option d is correct.