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Are two heads better than one?

eieio.games

21–30 of 78 posts

Re: Are two heads better than one?

#21
The second liar often gives you information you never wanted! But that is offset by the excellent information of when the liars agree. Fascinating.

I didnt't math during the thinking pause, but my intuition was a second liar makes it worse (more likey to end up 50-50 situation) and additional liars make it better as you get to reduce noise.

Is there a scenario where the extra liar makes it worse, you would be better yelling lalalallala as they tell you the answer?

Re: Are two heads better than one?

#22
post #6

I paused and wrote out all the probabilities and saw no way to improve beyond 80% - I scrolled down hoping to be proven wrong!

(I'm the author) I think there's an annoying thing where by saying "hey, here's this neat problem, what's the answer" I've made you much more likely to actually get the answer! What I really wanted to do was transfer the experience of writing a simulation for a related problem, observing this result, assuming I had a bug in my code, and then being delighted when I did the math. But unfortunately I don't know how to t…

I, erroneously, thought that "when Alice and Bob agree there's a 96% chance of them being correct, then surely you can leverage this to get above the 80% chance. What if we trust them both when they agree and trust Alice when they disagree?" Did some (erroneous) napkin math and went to write a simulation.

As I was writing the simulation I realized my error. I finished the simulation anyway, just because, and it has the expected 80% result on both of them.

My error: when we trust "both" we're also trusting Alice, which means that my case was exactly the same as just trusting Alice.

PS as I was writing the simulation I did a small sanity test of 9 rolls: I rolled heads 9 times in a row (so I tried it again with 100 million and it was a ~50-50 split). There goes my chance of winning the lottery!

Re: Are two heads better than one?

#23
The betting-voting distinction is interesting and was on my mind while I was reading it.

So much of this breaks down when the binary nature of the variables involved becomes continuous or at least nonbinary.

It's an example of a more general interest of mine, how structural characteristics of an inferential scenario affect the value of information that is received.

I could also see this being relevant to diagnostic scenarios hypothetically.

Re: Are two heads better than one?

#24

Bob isn't giving you any actionable information. If Alice and Bob agree, you're more confident than you were before, but you're still going to be trusting Alice. If they disagree you're down to 50% confidence, but you still might as well trust Alice.

Better than 50% confidence: they only lie 20% of the time, so when they disagree it's still 64% likely to be heads (.8 x .8)

No, it's 50% -- given that e.g. the flip is H, the base probability is both 16% for HT and 16% for TH.

Re: Are two heads better than one?

#26
It would be more straightforward to remove the permutations and just display the combinations and the symmetry between heads and tails. And solve it analytically Eg: if p is the probability that the NPC is correct

  P(A|AAAA) = p^4 
  P(A|BBBB) = (1-p)^4
Anyway, the apparent strangeness of the tie case comes from the fact that the binomial PMF is symmetric with respect to n (the number of participants) and n-k.

  PMF = (n choose k) * p^k * (1-p)^(n-k)
So when k = n/2, the symmetry means that the likelihood is identical under p and 1-p, so we're not gaining any information. This is a really good illustration of that; interesting post! (edit: apparently i suck at formatting)

Re: Are two heads better than one?

#27

Sailors in the past had a similar adage: “Never go to sea with two chronometers; take one or three.” They relied on precise clocks to calculate longitude.

I think it is different in the continuous case though, because you can average two (reasonably accurate) chronometers and get a better measurement. But we can't average true and false, at least not in the context of this problem definition.

But the chronometers are will sync with each other if you don't store them apart, which would result correlated noise that an average won't fix.

Re: Are two heads better than one?

#28
The triangulation effect with 3+ observers is fascinating, but there may be a weirder extension: what if the "third observer" isn't another person but the relationship coherence between two people?

Instead of three independent signals, you'd evaluate: given how Alice and Bob usually interact, does their agreement/disagreement pattern here tell you something? (E.g., if they're habitual contrarians, their agreement is the signal, not their disagreement.)

Take it further: human + LLM collaboration, where you measure the ongoing conversational dynamics—tone shifts, productive vs. circular disagreement, what gets bypassed, how contradictions are handled. The quality of the collaborative process itself becomes your truth signal.

You're not just aggregating independent observations anymore; you're reading the substrate of the interaction. The conversational structure as diagnostic.

Re: Are two heads better than one?

#29

Earlier quoted context omitted.

Better than 50% confidence: they only lie 20% of the time, so when they disagree it's still 64% likely to be heads (.8 x .8)

No, it's 50% -- given that e.g. the flip is H, the base probability is both 16% for HT and 16% for TH.

To complete the circle, now that we have winnowed the space down to these options, we would normalize them and end up with 0.16 / (0.16 + 0.16) = 0.5 = 50% in both cases.

The reason I'm not putting % signs on there is that, until we normalize, those are measures and not probabilities. What that means is that an events which has a 16% chance of happening in the entire universe of possibility has a "area" or "volume" (the strictly correct term being measure) of 0.16. Once we zoom in to a smaller subset of events, it no longer has a probability of 16% but the measure remains unchanged.

In this previous comment I gave a longer explanation of the intuition behind measure theory and linked to some resources on YouTube.

https://news.ycombinator.com/item?id=35796740

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