RE: When does statistics work?

[Rip Stauffer <rstauffer@bluefirepartners.com>]

I have been sort of relegated to the role of lurker lately, due to personal
and work priorities, but I had a couple of cents to add in here, thanks to
Bill Scherkenbach. He loaned me transcripts of a series Dr. Deming did at
Ford on the subject of Analytic vs. Enumerative studies. I just want to
quote a passage that seems pertinent here. 

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PJ: My problem is that....that, in effect, you're looking at these, though,
with extremely sophisticated eyeballs, extremely data-sophisticated
eyeballs. And is there any way that we can, in effect, articulate the
judgments that you use for deciding when, in an analytic situation, the data
should be supporting, closing on a decision, versus when it says, no, we
should keep looking?

Dr. D: ...I know the problem. You must know that I face it every other week.
Lots of them. 

I'll tell you a couple of tools that I find to be useful. One is a piece of
paper, and another was a pencil. And almost nobody has those tools on hand.
To save his soul from hell, he won't use them. He's gotta do it by computer,
or some statistical test.

Had some data. I can't call them clients. I try to find a little time to
help now and then. Doesn't make any difference where it was. They had
troubles. Asked if they'd collect some data on beginning, middle and end of
several batches....hardness of what comes out after vulcanization.

They did. And they plotted points...run charts, like this. And I said, now
look, that's awful hard for me to see anything there. This is beginning,
middle, end....beginning, middle, end. Awful hard to follow.

Let's just take the chart, plot it in a different way. Use a dot for the
beginning of the batch, an open dot for the middle--I don't care what you
use--and X for the end. Plotted sixteen batches in a row. Here they are.
One, two, three, four. Sixteen. In every case, the end was lowest of the
three, except for one tie. Just eyeball test. That stuff is either not mixed
or it's aging.

It's helped people. It's a simple graphical representation. Some of it's in
my book, chapter 13. Nothing unusual. Nothing spectactular. Nothing new.

Anybody can look and draw that conclusion. The stuff is aging, or it's not
mixed. One or the other.

They were engineers...so called. Had the privelege to study. It has helped
them. Least they said it did. Piece of paper and a pencil. Yes....

(new voice): If you had that data for sixteen in a row, where the end was
always at the lower hardness, could you then do a heads and tails
calculation on that?

Dr. D: Well hell fire, why do it? Make a lot of nonsense out of it? Why make
nonsense out of it? There it is. We have a job to do. Let's try to be
helpful.

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Best regards to all,

Rip

Rip Stauffer, Senior Consultant
BlueFire Partners
1300 Fifth St. Towers, 150 So. Fifth St.
Minneapolis, MN 55402
612-344-1027
rstauffer@bluefirepartners.com