Statistical process control

What is it?

Statistical process control (SPC) is ongoing analysis of data using control charts, histograms, and capability analysis. It is used to analyze and interpret data so that areas to improve become apparent. SPC can show the origin of a problem and demonstrate whether or not an improvement has been effective. These tools help identify causes of process variation, determine process stability and capability, predict the outcomes of processes, and plan for the future.

Why is it important?

Some of the benefits of SPC include:

  • Reduced costs
  • Reduced variability
  • Knowledge of process changes instantly
  • Reduced waste
  • Data-driven decisions

A process is said to be in statistical control when all special causes of variation have been eliminated and only natural (or common) cause variation remains. On a control chart, this is illustrated by data that falls within control limits and by the absence of non-random patterns or trends.

Statistical control is important because it shows what the process is capable of producing over time. Statistical control allows you to make predictions about how the process will run in the future, based on how it has run in the past. It helps you see if the process is currently capable of producing output that meets specifications 100% of the time.

How can PQ help?

PQ Systems provides training in the use of SPC and intuitive software to help you implement SPC offline and/or in a real-time environment.

Download a FREE SPC white paper

Download the free control chart white paper "Six SPC Charting Inefficiencies Solved" from PQ SystemsSix SPC Charting Problems Solved describes six time and money-wasting practices that can occur when companies implement statistical process control and provides tips on how to avoid them.


Statistical process control