A member of the volunteer fire department for Trenton, Ohio, decided to apply the control chart methodology he learned in his business statistics class to data collected by the fire department. He was interested in determining whether weeks containing more than the mean number of fire runs were due to inherent, chance causes of variation, or if there were special causes of variation such as increased arson, severe drought, or holiday related activities. The file Fire Runs contains the number of fire runs made per week (Sunday through Saturday) during a single year. Source: Data extracted from The City of Trenton 2001 Annual Report, Trenton, Ohio, February 21, 2002.
a. What is the mean number of fire runs made per week?
b. Construct a c chart for the number of fire runs per week.
c. Is the process in a state of statistical control?
d. Weeks 15 and 41 experienced seven fire runs each. Are these large values explainable by common causes, or does it appear that special causes of variation occurred in these weeks?
e. Explain how the fire department can use these data to chart and monitor future weeks in real time (i. e., on a week to week basis)?