It’s midnight, you’re at your favorite bar and the girl or guy of
your dreams walks through the door. You know you need to talk to them, but
immediately wonder how. You can use that
pick up line you planned a million times, you can fumble over some new line you
just learned, or you throw a hail Mary and just say “Hi, I’m [insert your name
nervously], and I think we should grab drinks.”
To all you young statisticians out there:
don’t try any of these. The problem with statistics is, we always think about the
long run; never the short run.
In
statistics, we use this term “the long run,” stemming from a really nerdy concept
called ”The Central Limit Theorem.” I’ll
leave the work of proving the theorem for our readers; suffice to say it
basically states that if we do something enough, we will eventually get the
actual permanent outcome.
To
some extent, our lives follow the central limit theorem in that our daily
routines tell us what we actually do. Think about your daily wake-up
time: you set your alarm for 6:30am, but rarely actually wake up at exactly that time; some
mornings you wake up at 6:35am and other mornings 6:25am. If we took all
those various wake-up times and graphed them, though, they would wind up normally
distributed with the mean at 6:30am. I’m stretching
the realities of statistics slightly, but this is the basic concept.
The point here is this: our expectations
are build around what is going to happen in the long run. But as the nervous
person at the bar, there’s no such thing as a long run; because of time
constraints this evening, a really short run is all we have.
Some life events and decisions – like
careers, friendships, and pick of our favorite foods – give us plenty of time
to play out. The sample size of these
events is large, so we know if our expected value is going to return positive
or negative results. Other things, however,
don’t have a long run. It’s the championship game and your team
needs 3 yards for a first down; if not, you lose the game (and your bet!). In the long run, the average NFL team goes 2 ½
yards on that play (believe me; I’m a statistician). But you need 3 yards, not 2 ½. There is no long run; the whole season comes
down to this short run.
I was recently at a casino, but needed to
get back home for a friend’s birthday party. Time was limited, so I couldn’t play the long
run. I took my $20, marched up to the
roulette table, put it on my birthday (12 and 6), and hoped the odds would be
in my favor. If I had time to sit down
and gamble, I may have hit those numbers in the long run – but I needed to
leave. Lucky for me, I wound up winning
on the one hand I played!
When we have time to think about things and
make informed decision, we should do what the long run dictates; when we don’t
have time, just go with it. When
statistical probabilities exist, use them, but don’t fear when they’re
absent. When thinking about where you’re going to live for the next
year, think through the probabilities. If you’re picking where to go
for dinner next week, think through the probabilities. But if you’re at a bar, and the person of your
dreams walks in – forget the probabilities.
In the short run, they probably don’t matter anyway.
