Control charts

Control  charts  are  tools  used  for  monitoring,  controlling  and  improving processes over time. These are applicable to administrative processes.

Figure: Control Chart

Steps to use control charts are:

1.  Collect initial data: This is the base line data for the process.

2.  Create the control chart: Plot the data. Calculate and plot the mean, lower and upper limits.

3.  Enter new data: A control chart is not just a snap shot of collected data.

It is a tool used over time to ensure that process remains in statistical control. Using the mean and control limits established by the baseline data, enter new data points and determine if they lie within or outside the control limits.

4.  Do not change the control limits based on new data unless the process changes. Completion of a process improvement effort to reduce random cause variation would be a reason to collect new data and establish a new mean and new control limits.