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Peripherally, I like using nuclear reactor design analogies for Aleatory vs. Epistemic. Aleatory is the inherent randomness of a system. You can characterize i

Peripherally, I like using nuclear reactor design analogies for Aleatory vs. Epistemic. Aleatory is the inherent randomness of a system. You can characterize it but it's often hard to reduce. For example, how much boron impurities are mixed into your steel at the time of manufacture. Epistemic is things that are knowable but you don't know with much certainty (because it's hard to measure), like the probability that an incident neutron at 1 MeV will inelasatically scatter off a Uranium-238 nucleus and emerge at 200 keV in some direction.

robbiep 8y ago
That might be really useful for you, but for those of us who don’t design nuclear reactors it is utterly meaningless - what are the consequences of each of the results and how much should I care about them? I would be blown away if more than 1 in 10,000 could understand what the consequences are of your statement. Care to share?
- duckerude 8y ago
  If I'm understanding it correctly, aleatory uncertainty is uncertainty you understand, and epistemic uncertainty is uncertainty due to lack of knowledge. Uncertainty about the outcome of an unbiased die roll is aleatory. You don't know what's going to happen, but that's because of inherent uncertainty, not because you don't know enough about the die. So while you can't be sure what the outcome will be, you can know that each outcome has a 1/6 probability, and you shouldn't expect to adjust that probability as you gain more knowledge. But uncertainty about the outcome of an election is epistemic, because it depends on a lot of present unknowns. If you run more polls you could reach a different, more accurate probability. Part or all of the uncertainty is because of things you don't know.
  - CompelTechnic 8y ago
    To continue the dice analogy- I can imagine a world where gambling sharks arrive at the roulette wheel in casinos, wearing hidden google-glass-ish devices, and place bets while the ball is in motion. Unbeknownst to everyone else, their device performed real time computation based on the position and velocity of the ball and wheel, and gave an output of a tight probability distribution (10% chance 25 red, 35% chance 29 black, 40% chance 12 red, 10% chance 8 black, 5% other). The sharks place bets based on these distributions, and make a bunch of money over the course of a few games. This raises the questions: 1. To the public (not the sharks), all of the possible outcomes of the game have equal probability. Would it be correct to say that all of their uncertainty regarding the outcome of the roulette wheel is aleatory? 2. To the card sharks, they DO have a model with knowledge of game outcomes. So should one say that the distribution output by the device is aleatory uncertainty, and the remaining uncertainty (the fact that there is a distribution instead of a single predicted outcome) in the system is epistimic? 3. #1 and #2 differ in presuming that such a device is present. In absense of such a device, or in general, in absense of a tested model, is it correct to say that all uncertainty is epistimic?
    - mercutio2 8y ago
      You don’t have to just imagine such a world. This actually happened in the 1970s (although it was a shoe computer and a team of well trained physicists, not Google Glass)! https://en.m.wikipedia.org/wiki/The_Eudaemonic_Pie https://en.m.wikipedia.org/wiki/The_Eudaemonic_Pie
JabavuAdams 8y ago
Wow, that's so much more clear and intuitive than using the six-sided die analogy. Thanks!
matt4077 8y ago
“Known unknowns” vs “unknown unknowns”. Despite the sniggering at the time, those terms are quite smart.
- dirtyaura 8y ago
  If with ”sniggering at the time” you refer to Donald Rumsfield’s use of the terms, it was his use of ”unknown known” that was bemusing

robbiep 8y ago

That might be really useful for you, but for those of us who don’t design nuclear reactors it is utterly meaningless - what are the consequences of each of the results and how much should I care about them? I would be blown away if more than 1 in 10,000 could understand what the consequences are of your statement. Care to share?

duckerude 8y ago
If I'm understanding it correctly, aleatory uncertainty is uncertainty you understand, and epistemic uncertainty is uncertainty due to lack of knowledge. Uncertainty about the outcome of an unbiased die roll is aleatory. You don't know what's going to happen, but that's because of inherent uncertainty, not because you don't know enough about the die. So while you can't be sure what the outcome will be, you can know that each outcome has a 1/6 probability, and you shouldn't expect to adjust that probability as you gain more knowledge. But uncertainty about the outcome of an election is epistemic, because it depends on a lot of present unknowns. If you run more polls you could reach a different, more accurate probability. Part or all of the uncertainty is because of things you don't know.
- CompelTechnic 8y ago
  To continue the dice analogy- I can imagine a world where gambling sharks arrive at the roulette wheel in casinos, wearing hidden google-glass-ish devices, and place bets while the ball is in motion. Unbeknownst to everyone else, their device performed real time computation based on the position and velocity of the ball and wheel, and gave an output of a tight probability distribution (10% chance 25 red, 35% chance 29 black, 40% chance 12 red, 10% chance 8 black, 5% other). The sharks place bets based on these distributions, and make a bunch of money over the course of a few games. This raises the questions: 1. To the public (not the sharks), all of the possible outcomes of the game have equal probability. Would it be correct to say that all of their uncertainty regarding the outcome of the roulette wheel is aleatory? 2. To the card sharks, they DO have a model with knowledge of game outcomes. So should one say that the distribution output by the device is aleatory uncertainty, and the remaining uncertainty (the fact that there is a distribution instead of a single predicted outcome) in the system is epistimic? 3. #1 and #2 differ in presuming that such a device is present. In absense of such a device, or in general, in absense of a tested model, is it correct to say that all uncertainty is epistimic?
  - mercutio2 8y ago
    You don’t have to just imagine such a world. This actually happened in the 1970s (although it was a shoe computer and a team of well trained physicists, not Google Glass)! https://en.m.wikipedia.org/wiki/The_Eudaemonic_Pie https://en.m.wikipedia.org/wiki/The_Eudaemonic_Pie

JabavuAdams 8y ago

Wow, that's so much more clear and intuitive than using the six-sided die analogy. Thanks!

matt4077 8y ago

“Known unknowns” vs “unknown unknowns”. Despite the sniggering at the time, those terms are quite smart.

dirtyaura 8y ago
If with ”sniggering at the time” you refer to Donald Rumsfield’s use of the terms, it was his use of ”unknown known” that was bemusing