The following messages came in through my Twitter (and Facebook) stream within a 15-minute span Monday morning:
Laura Howe: wow! metro is really quiet this am. hardly anyone on board for a monday morning.
Rick Murray: Want proof people are driving less: Metra has added a car to this train = 250 more folks doing the green thing downtown.
Two trains, two cities, two divergent opportunities to make an observation. That’s what we do, gather input and try to reorganize it into some semblance of understanding. It’s easier to remember conclusions than the steps it took to get there. It’s easier to remember the final score of a game than a comprehensive list of the plays. The trick is to remember the information that is significant.
Finding the Factor
In geometry, we have theorems – postulates that aren’t true by definition, but have been proven true by experience and derivation from other known truths. We fail when we skip to a new derivation without enough fact to support it. And we do that far too often.
Take Rick’s assertion. Is it indeed a sign of the times? Are there more commuters avoiding high gas prices? Is he basing this on a personal observation or just reading a news release from the operators of Chicago’s Metra?
Now look at Laura’s message. The Metro (DC) is eerily quiet. Does that entail a drop in ridership? Or is there a federal holiday underway, not uncommon for a Monday? Or are more people taking cars?
Truth is, we don’t know. We don’t have enough information. Such a message (or observation) remains strictly anecdotal out of context. Maybe Metra is adding a car in anticipation of behavior that will not materialize. Who knows?
Shortcuts Can Miss the Truth
All too often, we over-apply Occam’s Razor and end up buttressing our previously-held beliefs with new ‘evidence’ that might not apply. Take Laura’s case. How many reasons might there be for such a small number on her train:
- Holiday
- More people are driving cars than before
- Previous train was later than normal, giving a smaller “gap of opportunity” for riders
- Connecting train was late
- Erroneous report that trains were closed
- Laura got on an unusually empty car
Again, who knows? But human nature tells us that when we carry a powerful narrative, we’ll tend to lean in that direction. If you are just convinced that we’re in the worst economy ever, you might even believe no one is on the train because everyone else is at home after a layoff. If you’ve just heard about a flu outbreak, you might blame it on that. Or, if you know there is a parade that day, you might assume people are attending that event instead.
The misapplication of Occam’s Razor occurs when we choose to believe the simplest explanation that matches our preconceived worldview, instead of just the simplest.
And the simplest isn’t always correct – just more likely to be.
Now – for fun – please chime in with your ideas. Come up with your own possible explanations for why Laura’s train might have been unusually empty. Or, share your theories about why Metra is adding a car that might have nothing to do with “going green.”
[tags]Ike Pigott, Occam’s RazR, statistics, occam’s razor, postulates, theory[/tags]
A friend in Chicago lives next to a Metra station. He percieves an increase in the number of park ‘n’ ride cars, so I’m inclined to believe it’s a response to demand, not to greening.
Ike: When we hear hooves…think horses!? Or trains maybe? Iron horses???
Maybe, just maybe, Laura does, as my wife does, make casual, unsupportable assumptions that may or may not have any bearing on reality. Let us suppose that each observation was correct, that they were empirical and verified, that there were actually counts and that one time, one train, one day was statistically different than others. At that point, we could continue with your thesis–or observation, but until then, it’s just one perception, one train, one moment in time versus the same thing at another time and place.
In other words, just a personal hunch colored by all the personal GIGO -garbage in garbage out.
As a public transit professional, we know that to have real substance regarding decisions, we have to make real counts over time. Besides that, highway use and vehicle miles driven are declining and in general, public transit is up–waaaay up. So there is so much noise in these observations that they are likely of little value.
Have I added frustration to the conversation with these observations about these train stations and transportation rationalizations in our nation?
Thanks
One other note…I should have referred to both Laura and Rick as opposed to only Laura…and as an aside…”going Green” whatever that may be, has hardly ever played any significant role in transit use, thought it may be changing. It is more likely that people are making what might be described as Hobbesian choices based on simply getting hit harder with gas costs than with transit costs. At the same time, new transit systems, particularly urban rail have come on line in the last few years. What does this all have to do with Occam’s Razor or RaZr…..not sure, but we can all go along for the ride. Next stop coming up–but isn’t it always?
Ike,
For Laura: I hate to admit it, but what constitutes her “morning.” ;-P Did anyone consider that? I mean, if morning’s at 5am or 10am, this might clarify things a little more, wouldn’t you think?
For Rick: The additional train might have required servicing at the depot. It was bolted onto the main line, “towed” to the terminus, and as a result capacity was increased by an additional 250 spots for only *that* particular commute across town.
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Okay, I know it’s a bit preposterous, but I like to try anyways…