Re: Six Sigma and Shewhart

["Dr A D Burns" <mmedia@ozemail.com.au>]

In effect, this is what the "I" of a "PID" controller does. As long as a
process is encountering random variation, there is little reset windup and
little effect from the "I" component of the controller. When trends above
the mean, or runs occur, the integrating effect of the controller
progressively comes into play. It is not so effective with a trend around
the mean. Controllers also generally work on very short time intervals which
I guess makes them susceptible to auto-correlated data.

> mtribus@home.com writes:
>
> << Why don't you instruct the controller to leave things alone
>     unless it detects some reason for action, such as:
>         a point outside the control limits
>         seven points on one side or the other
>         a "ramp" of seven points
>         etc., etc.
>
>     Of course, then the controller would just call for help and
>     a human would intervene.  Maybe you can use artificial
>     intelligence to do better. >>

Tony Burns
MicroMultimedia
http://www.q-skills.com
mmedia@ozemail.com.au