Two assembly lines making the same item are monitored. After taking 20 consecutive samples from each line, the first assembly line has a grand average = 108.4 and average range = 2.21 based on subgroups of size 4 and the second assembly line has grand average =109.2 and average standard deviation =1.19 based on subgroups of size 5.

1. a) Which assembly line exhibits more consistency (less spread)? Support your answer statistically.

2. b) Construct appropriate control charts for both assembly lines.

3. c) If the specifications limits are set between 104.5 and 112.5, help the manager to

   identify which assembly line is better? Justify your answer.