A filling machine for a tea bag manufacturer produces approximately 170 tea bags per minute. The process manager monitors the weight of the tea placed in individual bags. A subgroup of n = 4 tea bags is taken every 15 minutes for 25 consecutive time periods. The results are stored in Tea3.
a. What are some of the sources of common cause variation that might be present in this process?
b. What problems might occur that would result in special causes of variation?
c. Construct control charts for the range and the mean.
d. Is the process in control?