Statistical Process Control (SPC)

Statistical Process Control,
As a way of achieving a goal,
Measures the change
From normal to strange
And enables a view of the whole

SPC can help understand
How things could better be planned
It can disprove presumptions,
But also affirm assumptions
And bring improvement closer to hand.

A process which is well-defined,
And measured over a period of time,
Will show variation,
And the right information
Will point to the causes behind.

Variation’s a terrible thing,
The way a system can swing,
From mean to extreme
Is a an awful regime
For us to be experiencing.

The upper control limit will be set,
(And the lower - lest we forget),
The average is shown
In the middle of the zone,
And the data’s ready to interpret.

Variation is special or normal,
Or in words a bit more informal,
One is unique,
An aberration or freak,
The other is much more conformal.

Special cause shows lack of control,
And that things have taken their toll,
The system will fail
It’s in the detail,
Unless we take charge of the whole.

When we know what the causes are,
And the plans needed to be back on par,
We can implement changes
To lower the ranges
And see how were doing so far.

If the plans have worked out okay,
And the changes are here to stay,
The limits will narrow,
Right down to the marrow,
And variation will be kept at bay.