The rock-off fairness fallacy (SOI cross-post)

I have a new blog! Dan and I are doing a joint blog over at thesubjectsofinterest.blogspot.com

Here's my latest post from over there.

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I've noticed that there is an increasing trend for people to resolve disputes or allocate resources using the game of Rock Paper Scissors. The procedure is sometimes called a 'rock-off', as in "let's rock-off for the last slice of pizza"

This procedure is fine in a two person game (assuming no one cheats), but I often see people happily submitting to three-way rock-offs. In these arrangements two people rock-off, then the third person plays the winner, and the winner of that second rock-off is declared the overall winner.

But this procedure is inherently unfair!

Imagine that John, Fred, and Mary are rocking-off for a slice of pizza. John and Fred play first. Mary plays the winner.

For John to win overall he has to win the first encounter against Fred and then a subsequent encounter against Mary. John has a .5 probability of winning the first time and .5 probability of winning the second time. .5 x .5 = .25, so he has a 25% chance of winning the pizza.

The same applies for Fred. He has to win first against John and then against Mary. Both times he has a .5 probability of winning, .5 x .5 = .25, so he too has a 25% chance of winning the pizza.

But Mary, she gets it easy. No matter what happens she only has to play once. Regardless of whether she's playing John or Fred she has a .5 probability of winning that rock off. So her chance of winning the pizza is 50%.

Mary has double the chance of winning overall because she only plays the winner. Great if you're Mary, bad if you're John or Fred.

Better to just draw straws.

Pet Peev - misuse of preparatory count ins

For a long time now, one my secret pet peevs has been the misuse of 'count ins'.

When a group of people are about to lift a heavy object, it is customary for someone to count "one, two, three, lift" so that everyone commences lifting at the same time. The point of such a count in is for the interval between each count to be equal so that everyone can anticipate exactly when the moment to 'lift' will be. The time that passes between "one" and "two", and between "two" and "three" tells you exactly how much time to expect between "three" and "lift". That's the point of a count in.

But how I usually hear people count in is this:

"Oooooooone...........(long pause)........twoooooooooo............(longer pause).............(and then when you least expect it) THREE! LIFT IT LIFT IT LIFT IT!"

What is the point of that?

A similar phenomenon is in the counting in of singing amongst non-musical types, particularly for the singing of Happy Birthday. Some will count a rapid "one, two, three" then a few seconds will pass before a very slow "haaaaaaaaaaaaaaaaaaaaaaaaapy biiiirthday to you" commences.

What's the point of that!?

In music, a count in is supposed to set the tempo. And besides, in the Happy Birthday song, the "happy" should actually start on the "three" not after it, because it's "birthday" that comes on the main beat. It should be "one two three, one two, Happy birthday to you..."

...i know i know, it's no big deal...it just annoys me. And thus concludes today's insane rant.

Longevity with a hard 'g'

The new leader of the Australian Liberal Party, Brendon Nelson, pronounces the word 'longevity' with a hard 'G'; 'G' as in 'gap' rather than 'G' as in 'gee wiz'.

What's with that?!

Pet Peeves - Misleading Facebook ID Photos

This might be a bit controversial, but is it just me, or is it really annoying when people use photos of people (or pets) other than themselves as their Facebook ID picture?

I mean, I can understand why people do it. Your Facebook profile picture is quite prominent, so you might like to put up a photo of something really important to you -- your children, a pet, Britney Spears.

But it's really confusing for the rest of us, particularly when you're trying to find someone who you've not seen in a while that has a common name.

What's even more confusing is when there's more than one person in the same picture with no way of telling which person is the owner of the Facebook profile.

Just something I had to get off my chest.