Tuesday, November 29, 2011

The Tuesday boy problem, in under 300 words

I saw a post this morning about something called the "Tuesday Boy Problem". It illustrates a really interesting and counterintuitive topic in probability, but it was written up in a frustratingly verbose, confusing, and ambiguous way. So I'm going to try to restate it more clearly.

Let's start from the basics. If a person on the street says to you, "I have two children," what is the probability that they're both boys? 1/4, since there are four possibilities, one of which produces two boys:

Now, imagine he says, "I have two children, and at least one of them is a boy." What is the probability they are both boys? Strangely, 1/3: we eliminate one of the four possible universes from the previous diagram, and one of the remaining three has two boys:

Here's where it starts getting strange: Let's say he says, "I have two children, and at least one of them is a boy born in an even-numbered month." You'd think that the information about his birth-month would be irrelevant, but believe it or not, it actually matters. We cross off 9 of the 16 possible worlds, and of the remaining 7, there are 3 with two boys. To put it another way, the even-month information eliminated half of the previous table's GB and BG universes, but only a quarter of its BB ones. So the odds are 3/7:

Finally, to return to the original problem: If the man says, "I have two children, and at least one of them is a boy who was born on a Tuesday", the probability that both are boys is a bizarre 13/27:

Kinda looks like a Scandinavian flag.

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Monday, March 21, 2011

Wild rumor: Conde Nast thinking of granting independence to reddit?

According to the Wall Street Journal's All Things Digital, Conde Nast is considering a spin-off of reddit.

This is the first I'm hearing of it, and it's being denied by the current admins, but I hope there's a grain of truth to the story.

Spinning reddit off would be a brilliant move, a total no-brainer. There are exactly zero synergies between reddit and any other Conde Nast property, and the site gains nothing from Times Square oversight. In fact, it would flourish even faster and more fully if freed from the policies that have been strangling it for years. ("Why does a site with a billion pageviews a month need more than one salesperson?" "What do you mean you want a $200 SSD hard drive? Anna Wintour gets by without one." "You want the company to pay airfare and hotels for your programming candidates? No way; BonAppetit.com just hired a perfectly good web designer without having to do that.") And imagine the motivating power of employee equity, which would actually be possible if reddit were an independent company.

The part of the rumor that makes no sense is where the Newhouse family is supposedly going to be selling big chunks of this spun-off company. In my time at reddit, I had extensive direct and indirect interaction with people named Newhouse, and I quickly learned that they're the only ones in suits who actually get it. The Newhouse family make for great reddit ownership... as long as they keep it as far as possible from people like this.

Executive summary: Spinning off reddit is a great idea, but selling it is the last thing you should do. No; keep reddit, and find some sucker to unload the rest of Conde Nast on.

Saturday, August 8, 2009


Check out this perfect souffle my wife made (using Alton Brown's recipe):

Friday, August 7, 2009

Hitchhikers Guide to the Galaxy "Order for Destruction" translated from the original Vogon

Infocom's classic interactive fiction version of The Hitchhiker's Guide to the Galaxy came with a fantastic assortment of feelies -- cool little trinkets and papers to encourage people to buy the game instead of just making a copy of their friend's.

Among them were an "order for destruction" of Arthur Dent's house and a similar-looking form that appeared to be an order for the destruction of Earth. However, it was written in an alien alphabet (which looks like a cross between Greek and Cyrillic), so there was no way to be certain.

I decided to take another look at it recently, to see if it was written in some kind of code. It turns out that it's just a simple cryptogram! I figured someone out there on the Internet must have deciphered this by now and posted it somewhere, but I can't actually find any other page about it on Google, so I guess this is the Internet debut. Drumroll please...

(BTW, all typos are reproduced verbatim. A few "uppercase" alien letters were undecipherable; those are represented with question marks.)


Be it known that on thi sday the 4th of October in the year of our Lord 1982 that by decree of the Domicile Demolition Department of Randomshire County, the residence of Arthur Dent of 122 Country Lane in The Town of Randomswich shall herewith be demolished, destroyed andotherwi se transformed into nondescript heap of pulverized rubble; thi sorder to be carried out postehaste, said resident(s) having evacuated said premiseswithin Now daysof the issuance of:

(Check one)
  • National Emergency
  • Black Plague hazard
  • Technical mattersfar to complex for the
    average layperson to begin to comprehend.
  • It'sin the way.
Said property hasbeen seized by Right of
Eminent Domain For Future Use As:

(Check One)
  • Parking Facilities
  • Shopping Mall
  • Wildlife Sanctuary
  • Hunting grounds
  • New officesfor Domicile Demolition
  • Vacant lot
  • Other (Please specify): Part of
    bypassbetween point A and point B.


We the undersigned do hereby authorize
the execution of thisorder through the
powersvested in u sby the State. God Save!

Commissioner, Domicile Demolition Department
Vice Commissioner, Domicile Demolition Department
Mail Clerk, Domicile Demolition Department

Copy 1. For issuance to Resident

There's also a few barcodes, though only one of them seems to parse. It evaluates to 051051010289, which seems to be a UPC symbol for a nonexistent product, though with a manufacturer ID belonging to Infocom.