1.5 Sigma Shift - Lean Six Sigma Glossary

1.5 Sigma shift refers to the long-term deterioration of process performance.

Process performance is not stable when looked at over a long period of time. The performance deteriorates in the long run as the variation in the processes increases inadvertently due to multiple factors.

According to Motorola, this movement in process performance in the long term is equal to 1.5 sigma shift. That is, if the short-term process capability is at 6 sigma level, the long-term capability will be at 4.5 sigma, after adjusting for the deterioration.

Motorola introduced the practice of reducing the calculated short-term sigma values of processes by 1.5 sigma to account for this deterioration of process performance to provide for a more realistic picture.

In the field of quality control and process improvement, 1.5 sigma shift refers to the long-term deterioration of process performance. Motorola introduced the term after observing that process performance is not stable when looked at over a long period of time. The performance deteriorates in the long run as the variation in the processes increases inadvertently due to multiple factors.

According to Motorola, this deterioration in process performance in the long term is equal to 1.5σ shift. This means that if the short-term process capability is 6σ, the long-term capability will be at 4.5σ, after adjusting for the 1.5σ shift. In order to provide a more realistic picture of process performance, Motorola introduced the practice of reducing the calculated short-term sigma values of processes by 1.5 sigma.

Causes, detection and measurement of 1.5 Sigma Shift

A variety of factors such as changes in the process, equipment malfunction, human error, lack of training and lack of maintenance can cause 1.5 sigma shift. These factors can lead to a gradual increase in process variation over time, resulting in a long-term deterioration of process performance. In addition, inadequate process design, which does not account for the long-term changes in the process can also cause this shift.

1.5 sigma shift can be detected by monitoring the process using statistical process control (SPC) tools such as control charts. Control charts are graphical representations of a process that show how the process is performing over time. They can be used to detect small shifts in the process mean, such as a 1.5 sigma shift, and also to detect long-term deterioration of process performance.

Correction

Once 1.5 sigma shift has been detected, it is important to correct the issue as soon as possible to prevent it from becoming a larger problem. The corrective action taken will depend on the cause of the shift. For example, if the shift is caused by changes in the process, the process should be corrected to bring it back to its original state. If the shift is caused by equipment malfunction, the equipment should be repaired or replaced. Training and maintenance are also important aspects to consider when correcting 1.5 sigma shift. Proper training of employees on the process and equipment can help prevent human error and lack of maintenance can lead to equipment malfunction.

In addition to these corrective actions, it is important to address the underlying causes of the shift. This includes evaluating the process design to ensure that it accounts for long-term changes in the process and implementing a system for identifying and addressing process changes.

Preventing 1.5 Sigma Shift

Preventing 1.5 sigma shift requires a proactive approach. Businesses should implement a continuous improvement program that focuses on identifying and addressing potential issues before they become major problems. This includes regular monitoring of the process using SPC tools, conducting regular equipment maintenance and training, and implementing a system for identifying and addressing process changes.

Additionally, businesses should also encourage a culture of continuous improvement, where employees are empowered to identify and address issues as they arise. This can be achieved through regular team meetings, employee training and development programs, and creating an environment where employees feel comfortable raising concerns and providing feedback.

1.5 sigma shift refers to the long-term deterioration of process performance as the variation in the process increases inadvertently due to multiple factors. It is important to detect and correct 1.5 sigma shift using SPC tools and take appropriate corrective actions, including training and maintenance. To prevent it from happening, businesses should implement a continuous improvement program, create a culture of continuous improvement, and evaluate and adjust the process design accordingly.

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Sachin Naik

Passionate about improving processes and systems | Lean Six Sigma practitioner, trainer and coach for 14+ years consulting giant corporations and fortune 500 companies on Operational Excellence | Start-up enthusiast | Change Management and Design Thinking student | Love to ride and drive