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Organizations want their organizations to perform with a predictable
range. If someone is making soda, the soda cans should contain approximately
12 ounces. If some cans produce only 11 ounces, customers and
the authorities will be upset and may lead to fines. If each can contains 12
ounces plus or minus .01 ounce, this may satisfy the company, customers, and
regulators.
So what causes process variation (a result different than the range
expected for a process)? Process Variation may be causes by a wide variety
of factors including
- resource variation (e.g. cans are slightly larger or smaller)
- human (e.g. setup employees did not set fill rate correctly)
- wear and tear (equipment is slightly worn out)
- Information system (e.g. did not translate targeted fill rate
correctly)
- line speed (line went too fast or too slow during filling
- temperature (different fill rates depending on temperature) --Never
fill your car with gasoline during hear of day or you will get slightly
less gas.
- new process
- new equipment
- new workers
- new materials
Organizations realize that variation will occur but
they want that variation to be negligible and they want to ensure the customer
does not see the variation.
Total Quality Management has show that all
processes have some variation. Some variation is normal and thus
worth controlling.
Processes that have small variation are said to
be "in control."
Large variation is caused by factors internal or
external to process.
Process Variation can take various shapes when you look at a traditional
bell curve:
- Average results on target and evenly distributed
- Average results off target but evenly distributed
- Results off target either higher or lower but evenly distributed
- Results off target but not evenly distributed
Processes that are evenly distributed are more predictable especially if
the range is small. Driving on Sunday afternoon to a destination is more
predictable than on Friday evening rush hour.
Call John Antos, Jim Brimson or Pat Dowdle at
972-980-7407 to find out more about Process Management.
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