Statistical Process Control (SPC) has become, in some ways, synonymous with process variation identification and monitoring. SPC uses statistical analysis to measure and control processes. It allows for the monitoring of stable processes and helps determine if any changes observed are the result of factors outside of inherent system variation.
SPC is also used to monitor the performance of processes per expectations, identify process capabilities, and track process changes. This information drives corrective actions that are taken and improvements that are made to processes. But where did SPC begin and is it still a useful technique today? Let’s find out.
A Brief History of SPC
The history of SPC is a long one with its roots dating back to the early 1920s. Walter A. Shewhart developed the concept of statistical quality control and control charts while working as engineer at Bell Laboratories. Two sources of variation, common cause and special cause, seeded the development of control charts; common cause, or stable chance, is the result of unknown factors while special cause, or unstable cause, is the result of specific and identifiable factors. Both causes triggered the need to plot variation data and determine identification.
Control charts reached their first heyday during World War II. Shewart’s work was used to integrate statistical quality control among Army divisions and the production of weapons and ammunition during this time. Another great champion of SPC, Dr. W. Edwards Deming, developed the concept further and even served as the first president of the American Society of Quality Control. Deming is also credited with bringing SPC to Japan’s manufacturing industry, after his introduction of the concept to the country in 1950.
SPC’s Place in Process Control Today
What about SPC today? SPC is still a critical aspect of Six Sigma especially in regards to variation reduction, quality control, and real-time implementation. With consumer standards ever on the rise, the technique’s capacity for eliminating defects and failure is essential.
Despite its indispensable capabilities, you may hear of SPC less today than you did in the past, especially during the 1990s. A common misconception is that SPC has been completely replaced by Lean Six Sigma and is just merely a tool within Six Sigma. Part of this misunderstanding lies in the poor explanation and instruction of the technique in some lesser-value Six Sigma certification programs. SPC is mischaracterized as a temporary activity only used to monitor and correct processes on occasion.
Learn the true value of SPC and how to master it alongside Six Sigma in NWCPE’s Six Sigma Program.
In reality, SPC has value for working with any process and improving quality of output. It has many uses including identification variation sources, cause of failure determination, daily variation reduction, and quality improvement effort monitoring. SPC has its place alongside Six Sigma as an means to generate and advance improvements and as a complement to Lean Six Sigma.
So, instead of thinking Lean Six Sigma and Six Sigma as replacements for SPC (and vice versa), it’s time to start thinking of all of the methodologies as the trifecta of continual improvement. To manage process variation and execute statistical process control, champions of Six Sigma and Lean Six Sigma must be equipped with the right tools. NWCPE’s Basic Statistical Methods (Module SS 502) and Statistical Process (Module SS 503), prepare professionals to control, monitor, and manage diverse processes. To broaden your process skill set, sign up for one or both of these courses today.