Lingo for layfolk?

On 6 Sep, 19:57, Jerry Avins <j...@ieee.org> wrote:
> On 9/6/2011 2:57 AM, Fred Marshall wrote:
>
> &#4294967295; &#4294967295;...
>
> > Seems to me that SPC isn't any different. Maybe you calculate mean and
> > variance of dimensions over some termporal window and then compare
> > results window-to-window. Isn't that essentially what a control chart
> > does with mean values?
>
> SPC isn't necessarily about flaws.

Correct. It's about *change*.

> Suppose a spec on a screw-machine
> part is 1' +- 1/64 (+-.015625) and parts have been consistently between
> .994 and .996. Now I begin to see some parts at .998 and none as small
> as .995. These are actually closer to spec, yet I might have cause for
> worry. SPC can allay my unease or prompt action. (The fact is, the tool
> bit is wearing.)

If something all of a sudden is closer to spec, it's not
necessarily a cause for worry, but rather a cause to investigate
why that change happened. If the cause can be identified, replicated
and controlled, one all of a sudden has an improved process.

Rune