Saturday, December 19, 2009


Unnecessary precision

We often see examples of insufficient precision, as when thirteen workers are killed in a building collapse, and a news report says that “more than a dozen workers died.” We can see that they’d want to hedge if there were still uncertainty about the number of deaths, but sometimes they just seem to think it sounds better this way. And if the number is high, it often makes more sense to report “more than six hundred” than to use the more precise “six hundred fourteen.” But when I hear “more than twenty,” I want to ask, “What does that mean? Twenty-one? Twenty-three?” If they’re uncertain, “at least twenty” makes that clearer.

On the other hand, there are times when there’s no value in more precision, and getting it just puzzles us. The Boston Globe’s excellent The Big Picture series has one of those in its 2009  in  photos set. The caption to photo 32 of part 3 says this:

A girl dives in a lake 100 km (62 miles) west of St. Petersburg, Russia, in this Aug. 7, 2009 photo.

Now, it’s unlikely that the lake is exactly 100 km from St Petersburg. It might actually be, say, 98 km away, or 103... or even 110. “100” is the sort of approximation we expect in a place such as this, a nice, round number that’s close enough for the purpose. So when someone punches that into a converter and gets 62.137 out in miles, we’d rather expect that to turn into “60 miles”. It would jar us to see the figure given to three decimal places, but it’s still kind of weird to see the the precision of “62”, given that the accuracy of the original “100” wasn’t good enough to warrant that. (And, conversely, seeing “62” might lead us to interpret “100” as being more accurate than it is.)

I saw a similar thing in an American airplane recently, where writing on an exit door said, “Caution: Door weighs 35.3 pounds.” That’s clearly a rounding of 16 kilograms (35.274 pounds) up to the next tenth of a pound, but why pick that particular precision? The point, here, is to warn someone who might have to manipulate the exit door about how heavy it is. “35 pounds” would be just fine for that — a quarter of a pound won’t make any difference, and if they think that matters then “36 pounds” would do as well. Is the door really 16 kg, and not, say, 15.8 or 16.3?

Think about what you’re stating (and converting), and use a precision that’s appropriate to the purpose. And if you’re worried about nitpickers, qualifiers such as “about” or “at least” are your friends.

While you’re looking through the 2009 in photos sets, I’ll point out two:
Part 1 photo 14 is very cool, and very hard to capture!
And part 3 photo 39 still makes me very happy.


Ray said...

I recently saw this gem in an email describing one of IBM's health care reimbursement plans:

Reimbursement Request forms received in good order by 11 a.m. Eastern time on any business day will typically be processed within 10 business days.

Another sign, on a mailing box on the floor where I work, has been puzzling me for the past 19 years:

Mail will be collected before 2PM each day

Barry Leiba said...

For the second one: you'd expect "by 2 p.m.", perhaps? In my experience, non-native English speakers can be confused by the expression "by [time]." I once arranged for someone to call me "by 11:00", because I had an 11:30 meeting. The guy called at 11:20, thinking that 11:00 was my first availability. "Before" or "after" is clearer.

Of course, since they give no early-bound, I suppose, theoretically, they could collect the mail at 10 a.m., and something you put in the box at 10:30 would wait 'til the next day. Oh, well. It wasn't that urgent, was it?

Yeah, "after" seems to be a more useful thing than "before" for this usage, hm?

Thomas J. Brown said...

And here I thought you would have a comment about the uselessness of the caption.

"A girl dives in a lake 100 km west of St. Petersburg, Russia."

Who cares that it's 100 km west of St. Petersburg? Is that really pertinent to understanding what we're looking at? How about something along the lines of: "A young Russian girl dives into a lake near St. Petersburg." Sure, 100 km isn't exactly "near" anything, but what other Russian landmarks will an American audience know?

The Ridger, FCD said...

I really don't understand what's wrong with Ray's first example. Is it the "typically"? That's obviously there to cover them in case things get busy.

The second one should just say "at 2 pm". Even if it's later some days, the point is to tell you when is the latest to put in mail to be sure it will be picked up that day.

Barry Leiba said...

I think the combination of (1) the gulf between the 11 a.m. deadline and the two week processing time and (2) the weaseling "typically" makes it quite laughable. Don't you?

Apart from that, it doesn't really even make sense. If you get your form in by 11 a.m., they'll process it in 10 business days. If you don't get it in until 11:30... what, it'll take 25 days, then? No, clearly it's meant to be 11 days, then. Doesn't the "typically" give them that without their having to specify a time? It's just stuff only a bureaucrat would love.

How about this for a stab at rewriting it?:
"Reimbursement Request forms are usually processed within 10 business days. Usually. But who really knows? Forms received after 11 a.m. will not begin the process until the next business day, because we'll have left for lunch by then. Forms with errors will be returned for correction, passed around the office for laughs, or just thrown in the trash. So be sure to get all the accounting codes right the first time."