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Control limits in SPC charts are extremely useful for many reasons. To put it simply and in the words of the IHI, control limits are: 'like traffic lanes that help you determine if your process is stable and predictable or not. If a process is not predictable, it cannot be improved. '

Statistical Process Control (SPC) Charts Rule 1 = Any point outside the control limits. Rule 2 = Seven consecutive points all above or all below the centre line, or all increasing or decreasing: Rule 3 = Unusual pattern or trends within the control limits:

The 8 Control Chart Rules RuleRule NamePattern1Beyond LimitsOne or more points beyond the control limits2Zone A2 out of 3 consecutive points in Zone A or beyond3Zone B4 out of 5 consecutive points in Zone B or beyond4Zone C7 or more consecutive points on one side of the average (in Zone C or beyond)4 more rows ? 12-Oct-2022

The three essential components of a statistical process control chart include a central line (CL) for the average, an upper control line (UCL) for the upper control unit and a lower control line (LCL) for the lower control unit.

What is an example of a statistical control? A statistical control is a process that is within an acceptable level of statistical variation. An example of a statistical control would be a manufacturing process that produces products with a weight that is within an acceptable range or variation.

Rule 8: A run of 8 consecutive points > 1? (either side) ? If we get 8 consecutive points > 1 sigma from the centerline (either side) then the special cause is available. ? In other words, 8 consecutive points with no points available in zone C (any side of the centerline).

Control Limits are Calculated by: Estimating the standard deviation, ?, of the sample data. Multiplying that number by three. Adding (3 x ? to the average) for the UCL and subtracting (3 x ? from the average) for the LCL.

The statistical process control (SPC) reports monitor the stability of a process. The charts in the reports show the data points in relation to the mean value, and upper and lower control limits.