Comments on: Meta Matters

By: Daniel Reeves

Daniel Reeves — Tue, 22 Nov 2016 20:11:00 +0000

In reply to nikana. Looks like all of letter.ly has died, in fact. Thanks for pointing it out!

By: nikana

nikana — Tue, 22 Nov 2016 19:57:00 +0000

By: Flexible Self-Control | Beeminder Blog

Flexible Self-Control | Beeminder Blog — Mon, 26 Mar 2012 03:48:43 +0000

[…] $800 offer, subject to some fine print [7]. As the dozen or so people who have collected on our $20 typo bounties will attest, we’re good for it. […]

By: Sharad Goel

Sharad Goel — Tue, 25 Jan 2011 19:27:56 +0000

Ah, I understand the confusion. Yes, I'm talking about a situation in which you're interested in repeatedly generating 50-50 outcomes, not just a single fair coin flip.

By: Lev Reyzin

Lev Reyzin — Tue, 25 Jan 2011 19:10:26 +0000

Sharad — I don’t get it. Once you have any die land on different numbers, you’re done (High->Low=Tails; Low->High=Heads). Is the MAB problem you set up to learn over time (ie. needing a fair coin many times) which coin is best?

By: Sharad Goel

Sharad Goel — Mon, 24 Jan 2011 22:28:00 +0000

Lev: for two rolls of the same die the payoff is 0 if they land on the same number, and 1 otherwise. Then the expected reward is the probability that the die results in distinct numbers on successive rolls (i.e., the probability that you can assert ‘heads’ or ‘tails’).

By: Lev Reyzin

Lev Reyzin — Mon, 24 Jan 2011 20:57:57 +0000

Sharad – what are the payoffs in this bandit problem?

By: Cris Iconomu

Cris Iconomu — Sat, 22 Jan 2011 22:16:40 +0000

use new rules:
– the face “facing” the thrower is the one that counts.
– if the die is pointing an edge at the thrower, use a ruler or something similar to push it agains the wall and force it to present a face (okay, this is a bit streched but you get the idea…)
no matter how the dice are loaded, by disregarding which face is up you eliminate the one factor participating in the “mechanism” – gravity. the rest is just … random
i asumed the use of cubic dice :)

By: Sharad Goel

Sharad Goel — Sat, 22 Jan 2011 15:15:07 +0000

Alex, I admit that it's a subjective call, and really, the two solutions are nearly identical. As an aside, if your goal is to efficiently generate 50-50 outcomes, instead of alternating between coins you could treat the situation as a multi-armed bandit, learning over time the better coin to flip.

By: Alex Strehl

Alex Strehl — Sat, 22 Jan 2011 03:27:54 +0000

fwiw, I still like my answer better than Bill’s, because it requires less rolls on average to halt (even if you’re required to roll both dice each turn).