What's the fundamental diff between common and special cause of variations?
Also,how to decide on which tools to use for identifying common and special causes respectively?
One should remember that common cause is “common” and that is not considered a defect while special cause is caused by a “special” reason (defect) which must be resolved in order for the process to run probably.
Dairy get regular supply of milk from various farmers. normal range of fat % from milk (knowing the breed of cow in the region) is between 3-5%
So when dairy receives milk supply they will measure the fat% for each batch and as long as fat is within range its ok it considered as common cause, say sometimes fat may be 3.6%, 4%, 4.3% etc and no action needs to be taken
however if the batch has 2% fat then its a special cause cause then some action has to be taken
PMP, PMI - ACP, SAFe Agilist
http://www.izenbridge.com/blog/7-effect ... ification/
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