Those dice aren’t loaded, they’re just strange

June 18, 2010 | Matt Asher

I must confess to feeling an almost obsessive fascination with intransitive games, dice, and other artifacts. The most famous intransitive game is rock, scissors, paper. Rock beats scissors.  Scissors beats paper. Paper beats rock. Everyone older than 7 seems to know this, but very few people are aware that dice can ... [Read more...]

A different way to view probability densities

June 12, 2010 | Matt Asher

The standard, textbook way to represent a density function looks like this: Perhaps you have seen this before? (Plot created in R, all source code from this post is included at the end). Not only will you find this plot in statistics books, you’ll also see it in medical ... [Read more...]

Tuesday’s child is full of probability puzzles

May 28, 2010 | dan

COUNTERINTUITIVE PROBLEM, INTUITIVE REPRESENTATION Blog posts about counterintuitive probability problems generate lots of opinions with a high probability. Andrew Gelman and readers have been having a lot of fun with the following probability problem: I have two children. One is a boy born on a Tuesday. What is the probability ... [Read more...]

How many girls, how many boys?

April 30, 2010 | Matt Asher

I found this interesting question over here at Here’s the question: If you have a country where every family will continue to have children until they get a boy, then they will stop. What is the proportion of boys to girls in the country. First off, there ...
[Read more...]

A von Mises variate…

March 25, 2010 | M. Parzakonis

Inspired from a mail that came along the previous random generation post the following question rised : How to draw random variates from the Von Mises distribution? First of all let’s check the pdf of the probability rule, it is , for . Ok, I admit that Bessels functions can be a ... [Read more...]

\pi day!

March 14, 2010 | M. Parzakonis

It’s π-day today so we gonna have a little fun today with Buffon’s needle and of course R. A well known approximation to the value of $latex \pi$ is the experiment tha Buffon performed using a needle of length,$latex l$. What I do in the next is ... [Read more...]

Example 7.26: probability question

March 8, 2010 | Ken Kleinman

Here's a surprising problem, from the xkcd blog.Suppose I choose two (different) real numbers, by any process I choose. Then I select one at random (p= .5) to show Nick. Nick must guess whether the other is smaller or larger. Being right 50% of the ...
[Read more...]

Counterintuitive Results in Flipping Coins

August 28, 2009 | Yihui Xie

oin-flipping is a rather old topic in probability theory, so most of us think we know very well about it, however, the other day I saw a question about this old topic (in David Smith’s REvolution?) which was beyond me expectation: how many times do we need to flip ... [Read more...]
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