Out Of Control Conditions On A Control Chart
A control chart is a statistical tool that helps to monitor the quality of a process over time. It is a graph that displays data points along with control limits that show the expected variation in the process. The purpose of a control chart is to identify when a process is moving out of control so that corrective action can be taken before the product or service is affected.
In order to use a control chart effectively, it is important to understand the different types of out of control conditions that can occur. These conditions are known as special causes of variation and are different from the expected random variation that occurs in any process.
Types of Out Of Control Conditions
There are several types of out of control conditions that can occur on a control chart. These include:
1. Shifts
A shift is a sudden change in the process mean. This can be caused by changes in equipment, raw materials, or personnel. When a shift occurs, the data points on the control chart will move above or below the control limits.
2. Trends
A trend is a gradual change in the process mean over time. This can be caused by changes in the process or the environment. When a trend occurs, the data points on the control chart will move in a consistent direction.
3. Cycles
A cycle is a predictable pattern of variation that occurs over time. This can be caused by seasonal changes or other recurring events. When a cycle occurs, the data points on the control chart will move up and down between the control limits.
4. Outliers
An outlier is a data point that falls outside of the control limits. This can be caused by measurement error or other factors. When an outlier occurs, it indicates that something unusual has happened in the process.
Dealing With Out Of Control Conditions
When an out of control condition occurs on a control chart, it is important to take corrective action to bring the process back into control. The first step is to investigate the cause of the condition and determine what changes need to be made.
Once the cause has been identified, the next step is to implement the necessary changes and monitor the process to ensure that it stays in control. This may involve making adjustments to equipment, changing procedures, or providing additional training to personnel.
It is important to remember that control charts are a tool for continuous improvement, not just for monitoring. By identifying out of control conditions and taking corrective action, the process can be improved over time to produce better quality products or services.
Conclusion
A control chart is a powerful tool for monitoring the quality of a process over time. By understanding the different types of out of control conditions that can occur, you can take corrective action to bring the process back into control and improve the quality of your products or services. Remember to use control charts as a tool for continuous improvement, not just for monitoring.