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Shewhart control chart rules TestRule11 point is outside the control limits.28/9 points on the same size of the center line.36 consecutive points are steadily increasing or decreasing.414 consecutive points are alternating up and down.4 more rows

List of the eight Nelson Rules for interpreting control charts One point above UCL or below LCL. Two points above/below 2 sigma. ... Four out of five points above/below 1 sigma. Eight points in a row above/below the center line. Six points in a row ascending or descending (trend)

How do I know if my process is in-control? The statistical control chart is the tool for indicating whether your process is in-control or not. If your data points are falling within the calculated control limits and are random, that's an indication that your process is in-control.

Basic Procedure Determine the appropriate time period for collecting and plotting data. Collect data, construct your chart and analyze the data. Look for "out-of-control signals" on the control chart. When one is identified, mark it on the chart and investigate the cause.

The following rules can be used to properly interpret control charts: Rule 1 ? One point beyond the 3 ? control limit. Rule 2 ? Eight or more points on one side of the centerline without crossing. Rule 3 ? Four out of five points in zone B or beyond. Rule 4 ? Six points or more in a row steadily increasing or decreasing.

Nelson rules RuleDescriptionProblem IndicatedRule 8Eight points in a row exist, but none within 1 standard deviation of the mean, and the points are in both directions from the mean.Jumping from above to below while missing the first standard deviation band is rarely random.7 more rows

Points Beyond the Control Limits Action should be taken to find the special cause and permanently remove it from the process. If there is a point beyond the control limits, there is no need to apply the other tests for out of control situations.