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Comment As always, ambiguous language (Score 3, Insightful) 981

by natbrooks (#32729686) Attached to: The Tuesday Birthday Problem

"I have two children, one of whom is a son born on a Tuesday. What is the probability that I have two boys?"

As always, the challenge is the assumptions intentionally hidden in the problem statement.
"I" - was your family chosen at random, and if so, from what set?
"two children" - exactly or at least?
"one of whom" - exactly or at least?
"son" - was the sex to say chosen at random, or did you pick a child and announce his/her sex?
"Tuesday" - was the day chosen at random, or did you pick a child and announce his.her birthday?
"What is the probability..." - Some parent you are! Don't you know the sex of your own children?

Simply and honestly reveal the assumptions and the math is straightforward.

"Given a family, chosen at random from the set of all families that have exactly two children and have at least one son born on a Tuesday, what is the probability that both children are boys?"

To make the math easier, let's start with 196 families with two children, with the expected mix of boys and girls. 49 (25%) have two boys and 98 (50%) have a boy and a girl. Of the 98 boy-girl families, 84 do not have a Tuesday-Boy, leaving 14 that do. Of the 49 boy-boy families, 36 do not have a Tuesday-Boy, leaving 13 that do. That leaves a total of 27 families, of which 13 have at least one son born on a Tuesday.
So the probability is 13/27.

Reveal different assumptions, and the answer changes.
Power

Creating Electric Power From Light Using Gold Nanoparticles 77

Posted by Soulskill from the nanite-power-supply dept.
cyberfringe writes "Professor of Materials Science Dawn Bonnell and colleagues at the University of Pennsylvania have discovered a way to turn optical radiation into electrical current that could lead to self-powering molecular circuits and efficient data storage. They create surface plasmons that ride the surface of gold nanoparticles on a glass substrate. Surface plasmons were found to increase the efficiency of current production by a factor of four to 20, and with many independent parameters to optimize, enhancement factors could reach into the thousands. 'If the efficiency of the system could be scaled up without any additional, unforeseen limitations, we could conceivably manufacture a 1A, 1V sample the diameter of a human hair and an inch long,' Prof. Bonnell explained. The academic paper was published in the current issue of ACS Nano. (Abstract available for free.) The significance? This may allow the creation of nano-sized circuits that can power themselves through sunlight (or another directed light source). Delivery of power to nanodevices is one of the big challenges in the field."
Patents

Patent Markings May Spell Trouble For Activision 82

Posted by Soulskill from the almost-rocket-docket dept.
eldavojohn writes "If you pick up your copy of Guitar Hero and read the literature, you'll notice it says 'patent pending' and cites a number of patents. A group alleges no such patent pends nor are some of the patents applicable. If a judge finds Activision guilty of misleading the public in this manner, they could become liable for up to $500 per product sold under false patent marking. The patents in question seem to be legitimately Guitar Hero-oriented, and little is to be found about the mysterious group. The final piece of the puzzle puts the filing in Texas Northern District Court, which might be close enough to Texas Eastern District Court to write this off as a new kind of 'false patent marking troll' targeting big fish with deep coffers."
Apple

Has Apple Created the Perfect Board Game Platform? 531

Posted by kdawson from the triple-word-score dept.
andylim writes "recombu.com is running an interesting piece about how Apple has created a 'Jumanji (board game) platform.' The 9.7-inch multi-touch screen is perfect for playing board games at home, and you could use Wi-Fi or 3G to play against other people when you're on your own. What would be really interesting is if you could pair the iPad with iPhones, 'Imagine a Scrabble iPad game that used iPhones as letter holders. You could hold up your iPhone so that no one else could see your letters and when you were ready to make a word on the Scrabble iPad board, you could slide them on to the board by flicking the word tiles off your iPhone.' Now that would be cool."
Music

Student Orchestra Performs Music With iPhones 65

Posted by samzenpus from the there's-a-symphonic-app-for-that dept.
A course at the University of Michigan ends with a live concert featuring students using iPhones as instruments. “Building a Mobile Phone Ensemble“ teaches students to code musical instruments for the iPhone, using the Apple-provided software-development kit. Georg Essl, assistant professor of computer science and music, says, "What’s interesting is we blend the whole process. We start from nothing. We teach the programming of iPhones for multimedia stuff, and then we teach students to build their own instruments.”
Books

Fraud Threat Halts Knuth's Hexadecimal-Dollar Checks 323

Posted by timothy from the sobering-thought-about-checks-in-general dept.
Barence writes "You may be aware of Donald Knuth, the creator of TeX and author of The Art of Computer Programming, who used to post checks to anyone who spotted an error in one of his books — one hexadecimal dollar, or $2.56. No one cashed them though. This blogger has two of them proudly on his wall, but the sad news is that modern day bank fraud has put a stop to Knuth's much-loved way of keeping his books free of errors." (Here's Knuth's own post about the sad change.)

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