Home : QC Flag Detection Rules
Q14222 - INFO: QC Flag Detection Rules

In both the QC Report and Variable Analysis Graphs data can be analyzed for QC or SPC Flags.  In a classic SPC Chart we are trying to detect variation beyond the normal chance variation of the process.  These variations are called Special Causes. 

The main purpose of a SPC Chart is to detect a Special Cause (i.e. a process that may not be in control).  SPC charts allow you to detect potential problems before they become obvious.   Once a special cause is identified, we can then take actions to remove it. 

The following rules are generally accepted in interpreting SPC/QC Charts.

All points above or below the Upper and Lower Control Limit: Checks each value against the Upper and Lower Control Limit.

??? Consecutive points are above or below the Warning Limits: Default 2. If 2 or more consecutive points are above or below the Warning Limit the data is flagged.

??? Consecutive points are on one side of the mean: Default 7. If 7 or more consecutive points fall on the same side of the QC Mean. QC Mean is the average of the data set if calculated or can be manually entered as a setpoint.

??? Consecutive points are sloping in one direction: Default 5. If 5 or more consecutive points are sloping in the same direction (i.e. values of 1,3,4,7,9 are sloping up for 5 points since each point is greater than the previous point).

Related Articles
No Related Articles Available.

Article Attachments
No Attachments Available.

Related External Links
No Related Links Available.
Help us improve this article...
What did you think of this article?


Tell us why you rated the content this way. (optional)
Approved Comments...
No user comments available for this article.
Created on 6/20/2014 2:05 PM.
Last Modified on 6/23/2014 4:50 PM.
Last Modified by Scott Dorner.
Article has been viewed 2288 times.
Rated 0 out of 10 based on 0 votes.
Print Article
Email Article