"Doug Miller" wrote in message
et...
In article , "Ed Huntress"
wrote:

Think of this as something like teaching a man to fish. Now you know where
the data is, and how neatly they lay it out for you. The thing to do with
it
is to plunk it into Excel and let it draw a curve. If there's a kink in
the
curve soon after the CCW law was enacted, something happened. If there's
no
kink, it means that the CCW law had no effect.

Phooey. A simplistic single-variable analysis like that means nothing of
the
sort, either way. All it means is that _if all other factors were equal_
then
the CCW law had 'x' effect (or failed to have 'y' effect).

--
Regards,
Doug Miller (alphageek at milmac dot com)

It's time to throw all their damned tea in the harbor again.

No, Doug, on two counts. First, the claim we're testing is that a single
variable (enactment of a CCW law) had a measurable effect. The authors of
the quote Gunner posted made that claim.

If there were other, confounding events going on at the same time, the curve
would have short-term lumps or kinks in it. It does not. Furthermore, you
can test it further (I did) by overlaying it with national and/or regional
data, where there were no new CCW laws in the other states. If the CCW law
had an effect in Texas you would see a kink or lump in the curve and no
comparable lumps in the other states.

Second, if there were countereffects from other variables, they would
produce lumps, as well. The chance that one variable would *exactly
counterbalance* the CCW law, and thus produce the *illusion* of a smooth
curve, is so vanishingly small that you'd might as well forget it. One
effect would have to turn on just as the other one turned off, and to
exactly the same degree and with the same trend. Your chances of winning the
lottery are greater.

This is standard curve-testing stuff in economics. It's a first cut, and you
have to look closer before putting your money on a bet. But it's a very
effective way to see if something happened or it didn't. In this case,
nothing happened.

BTW, I ran the same data for Florida over the past 15 minutes, around the
year 1987, when they enacted their CCW law. But I'll leave that as an
exercise for anyone who's interested. d8-)

--
Ed Huntress