How do you apply SPC to non-manufacturing processes such as service delivery or customer satisfaction?

2 Collect and organize the data

The next step is to collect and organize the data that reflects the performance and quality of the output. You need to decide what type of data to collect, how often to collect it, and how to store and display it. The type of data can be either variable or attribute. Variable data is continuous and can be measured on a scale, such as time, weight, or speed. Attribute data is discrete and can be counted or categorized, such as yes/no, pass/fail, or good/bad. For example, if you want to measure the customer satisfaction rating, you can use a variable data such as a score from 1 to 10, or an attribute data such as satisfied or dissatisfied.

3 Choose and construct the SPC chart

The third step is to choose and construct the SPC chart that best suits the type of data and the purpose of the analysis. An SPC chart is a graphical tool that plots the data over time and shows the variation and trends in the process. Some of the most common types are the X-bar and R chart for variable data with subgroups of samples, the p-chart for attribute data with proportions or percentages, and the c-chart for attribute data with counts. When constructing an SPC chart, you need to calculate the mean, standard deviation, and control limits of the data. The control limits are boundaries that indicate normal variation in the process; any data points that fall outside these limits are considered outliers or signals that something is wrong with the process.

4 Analyze and interpret the SPC chart

The fourth step is to analyze and interpret the SPC chart to identify the patterns and causes of variation in the process. You need to look for any data points that are outside the control limits, or any trends or cycles that indicate a change in the process. These are signs of special cause variation, which means that there is a specific and identifiable reason for the variation, such as a faulty machine, a human error, or a change in customer demand. You need to investigate and eliminate these causes to improve the process. On the other hand, if the data points are within the control limits and show no significant trends or cycles, it means that there is only common cause variation, which is inherent and unavoidable in any process. You need to accept this variation and focus on maintaining the process.

5 Implement and monitor the improvement actions

The final step is to implement and monitor the improvement actions that result from the analysis and interpretation of the SPC chart. You need to document and communicate the actions, assign responsibilities, and track the progress and results. You also need to update and review the SPC chart regularly to see if the actions have reduced the variation and improved the quality and performance of the process. If not, you need to repeat the steps until you achieve the desired outcome.

SPC is a powerful and practical method of quality improvement that can be applied to any process, whether it is manufacturing or non-manufacturing. By using SPC charts and tools, you can monitor and control the variation in your process, and identify and eliminate the causes of poor quality or performance. This way, you can enhance your service delivery or customer satisfaction, and achieve your business goals.

6 Here’s what else to consider

This is a space to share examples, stories, or insights that don’t fit into any of the previous sections. What else would you like to add?