In class we talked about the differences between natural variations and assignable variations.  Variations that affect all parts of production are natural variations or common causes.  Variations caused by a specific reason are classified as assignable variations or special causes.  I’m sure you’ve all seen the movie Elf.  If not, you must go out and see it because it is the perfect example for variations.  Buddy is a human who was raised by elves so he believes he is one too.  When the elves are preparing to make toys for the holidays, Buddy always under performs in his quota.  In this case, Buddy would be the special cause since he is sub par with his products and numbers.  So what does the management decide to do with a self-proclaimed cotton headed ninny muggings?  Well, in Buddy’s case, they keep him as a toy tester and I think we all know the rest of the story.

As a manager in the real world, things aren’t as easy as running Santa’s toy factory.  Variations can be tricky to determine and how to handle them because ever decision made costs the company money.  Had the problem for a production facility been a common cause, there would have been certain tests to tell whether the process was in or not in control.  In special causes it is usually more difficult to determine because one specific issue can lead to problems.  To deal with special causes you get rid of the bad and incorporate the good.  Control charts are looking to determine problems are natural or assignable variations.  Based on the shape of the curve, we can tell what the problem is likely caused by.  If Santa wanted to find where his variations were coming from he could look at the frequency, size, and consistency of the curves.  Clearly Buddy would obviously be inconsistent with the rest of the chart and Santa would then find his problem.  Although I’m sure that in the real world, the cotton headed ninny muggins, or a poor performing employee, wouldn’t be sent to the back to test jack-in-the-boxes.