Understanding Statistical Process Control (SPC)

Statistical process control (SPC) is a technique used to monitor processes to ensure they are under control. SPC can be used for many different types of industries, including manufacturing and food production.

In this article, we'll cover statistical process control, how it works, and why it's so important. We'll also discuss some examples of applications where SPC has been put into practice so you can see how effective this method is at improving operations overall!

What is statistical process control (SPC)?

Statistical process control (SPC) is a technique used to monitor processes and manage their quality on an ongoing basis. It can be used to detect small shifts in overall variability and changes in dispersion so that the process can be monitored and adjusted accordingly.

The SPC process controls the manufacturing or processing of a product by comparing current performance with previously obtained results. The statistical techniques used during this comparison are based on comparing actual results with expected values predicted from formulas or tables known as control charts (CC).

The techniques behind SPC

SPC is a set of techniques that can be used to monitor processes and detect changes in their behavior. The techniques are based on control charts, which show whether a process is under control by comparing its performance to a target value or goal.

Control charts are divided into three types −

  • Process Control is used to monitor and improve the quality of a specific process or step in a production system. The chart will show the percentage of completion for each stage of the process, and it can be used to identify problems early on so they can be corrected before they cause serious damage.

  • Channel Control ensures that products arrive at their destination in an acceptable condition. Charts will display how many defective items were sent out, how long products took to reach their destinations, and other related information, such as trends over time. This type of control helps you optimize your distribution channels while minimizing losses caused by defects or accidents.

  • Lastly, Performance Control charts are often included with inventory management systems in order to evaluate business performance based on key metrics such as sales volume or profits.

How SPC works?

Statistical process control (SPC) is a widely used application in manufacturing and engineering to monitor the quality of processes and maintain setup within tolerances.

It is also commonly used to create alerts when deviations from desired parameters occur so corrective actions can be taken as soon as possible. SPC allows for the efficient allocation of resources by providing early warning signs of potential problems.

When data is collected from various sensors or devices throughout a manufacturing or engineering process, it's important to analyze the data carefully in order to identify any trends or patterns.

This information can then be used to establish trigger points − specific values or conditions at which routine checks should begin automatically. If abnormalities are detected at these trigger points, action will usually be taken immediately (for example, adjusting machine settings). By establishing clear rules and procedures upfront, manufacturers and engineers can avoid costly errors down the road.

If the process goes out of control, it is possible to identify and solve the problems in order to bring the process back into a state of control.

  • Identifying Problems − The most important method for identifying problems is through visual inspection. This is done by observing all aspects of your product or service at different points during its manufacturing process and identifying any issues that could have been prevented by proper planning or management decisions.

  • Solving Problems − After identifying potential problems, it's time to solve them! To do this effectively, you'll need a data analysis tool that can help track down sources (and causes) behind each issue so that you can take action accordingly−and hopefully prevent future occurrences altogether.

  • Bringing Process Back Into State Of Control Once All Issues Are Resolved − Once all issues have been identified & resolved successfully using proper techniques such as SPC & Quality Management System (QMS), then finally put everything back together again before proceeding further into the production stage where final products will reach consumers' hands upon completion.

One way SPC can be used is by managing the production quality of a product on an ongoing basis. This is done by measuring several variables which affect the process −

  • Variables that affect the speed of the process (such as production time)

  • Variables that affect the quality (such as defects)

  • Variables that affect costs (such as material cost).

Types of charts used in SPC

There are mainly three charts used in Statistical Process Control −

1. Control Charts

They are used to monitor processes. They are not particularly useful for monitoring processes that have low variability, but they can be very useful when there is a high degree of variability or when the process has been ongoing for some time.

For example, if you are measuring the quality of your product and find out that most products don't meet your standards, then it would be appropriate to use control charts on your production line in order to identify potential problems before they occur. Control charts are also ineffective at monitoring short cycles like those found in manufacturing environments where products may change quickly (e.g., one day).

2. Range Charts

A range chart is useful for detecting small shifts in overall variability. The range chart shows the difference between the highest and lowest values, and it's useful for detecting changes in dispersion (the spread of data).

The range chart can also detect large shifts in overall variability. This is important because it helps you identify when something has changed so that you can take action quickly and prevent problems from occurring further down the line.

3. Standard Deviation Chart

The standard deviation chart can detect large changes in dispersion.

It is used to measure the dispersion of a data set or process. It is also one of the most widely used probability distributions.

The range, mean and standard deviation are all important values that must be known when performing statistical analyses on any data set or process. An example of how you would use an SPC chart would be if you wanted to find out if there had been any shift in your average sales per month over time.


SPC is a useful tool for making information−based decisions. It can help you to identify problems in processes and solve them before they become serious enough to affect the quality of your products.

Statistical process control helps ensure that products are produced according to set standards. In many cases, management may choose this method because it is more practical and reliable than other methods. Besides, it has been proven to keep inventory costs down as well. All in all, this information about SPC could prove useful for anyone who manages any sort of production line at their workplace.