Unit 7: Statistical Process Control
Hannah Hohendorf
Assignment Date: November 16, 2017
The business of rising, getting ready, and arriving for work from Monday through Friday takes time. After mapping the amount of time (in minutes) that it takes for 15 consecutive work days, it was discovered that the mean time from rising to working is 53 minutes. This time is spent driving, walking dogs, showering and more for the day which are all necessary activities but could be improved upon not only making the time shorter, but also more productive. The following paragraphs will describe the data gathered, the process steps and improvements that should be made to optimize mornings.
The process was as follows: the individual would wake up, take a shower, get dressed, take the dogs outside, feed and water the dogs, brush teeth, pack bag, go down to the lobby for coffee, and drive to work. The data was gathered over 15 days by the individual marking the time that they woke and the time they arrived at work. These times were then converted to a number of minutes and the mean calculated. Following calculation of the mean, a run chart was created showing the total minutes charted each day.
Next, a control chart was created by adding an upper control limit (UCL) and lower control limit (LCL). These were designated by calculating the standard deviation of the 15 data points, then multiplying that standard deviation by 3 (3SD). Finally, the value for 3SD was added to the mean for the UCL (72 minutes), and subtracted from the mean for the LCL (34 minutes). Once calculated, the UCL, LCL, mean and data points were graphed on a run control chart and analyzed. From this process, common and special causes of variation were identified.
A common cause of variation is a cause that occurs as part of a process and allows the data from the process to be predictable (Joiner, 2014). The common causes of variation within this process include elevator wait times, shower time, time from waking to rising from bed, finding clothes to wear, finding items to pack for bag and traffic delays on the ride to work.
A special cause of variation is a cause that often occurs from an external source which allows the process to become unpredictable (Joiner, 2014). Special causes of variation for this process could include malfunctioning elevators, lost car keys or ID badge, and a dead car battery.
The run control chart showed the data points all falling within the UCL and LCL indicating that common cause variation was occurring. This meant that the process was stable and that the improvement strategies that would work best were stratifying data, experimenting, or disaggregating the process (Joiner, 1994).
For this process, experimenting would be a good option for implementing improvements because the impact for failure is low. Also, the fix should be deep so that the process is improved and then maintained. To engineer a deep fix, there are three levels of fixes that should be implemented including level 1, level 2, and level 3.
A level 1 fix is one that corrects a problem in the moment which is often used for special cause variations (Joiner, 1994). For instance, taking the train if the car is inoperable, which can be facilitated by signing up for the employee benefit that grants access to the trains.
A level 2 fix is one that corrects step in the process (Joiner, 1994). For instance, a lot of time is spent looking for clothes to wear. If clothes were set aside each night, this search time would be eliminated leading to a reduction in the overall process time.
A level 3 fix is one that corrects the system in which the process operates (Joiner, 1994). For instance, the individual goes to bed late in the evening and early morning which has led to persistent sleep-deprivation. This lack of sleep affects the time and speed at which the individual rises and proceeds to go through the steps for preparing to go to work. If the person starts to get at least 8 hours of sleep a night, they will be able to go through the process at a faster more efficient pace than if they were sleep-deprived.
Therefore, if the employee signs up for access to the trains, lays out their clothes each evening and gets at least 8 hours of sleep each night, then a reduction in the mean time of the rise-to-work process should occur. Furthermore, they will be better prepared should an automobile issue arise.
Overall, the process that this individual follows from rising to work is stable with common cause variation occurring over the past 15 days. By implementing three levels of fixes, the process should improve with a reduction in the mean time spent each morning getting ready and driving to work as well as preparing the individual for a special cause of variation with their car. This process and proposed changes illustrate the value of collecting data and statistical process control.
References
Joiner, B. L. (1994). Fourth generation management: The new business consciousness. New York: McGraw-Hill.