23 ms·

If You Say Something Is “Likely,” How Likely Do People Think It Is?

131 points by randomwalker 8y ago

twiss 8y ago
Using numbers for probabilities is not a panacea either, when those numbers are not the result of a calculation. One person might say "99% of the time" to mean "almost always", and another person might say "9 out of 10 times" to mean exactly the same thing. The problem is that it's hard to estimate the probability of something that you know happens "almost always" without doing the counting, which most people don't do. And hence it's difficult to gain an intuition for what 99% means exactly. Furthermore, there is also the possibility that two people share the same intuition about a given word/phrase, but then disagree about which number describes that intuition. This could account for part of the results of this paper.
- c3534l 8y ago
  A good example of this is ratings on Amazon. You can give up to five stars, but most people just give 1 or 5 depending on if they were satisfied or dissatisfied. Additionally, people confuse precision for certainty and will perceive an estimate of 89.1% as more accurate than 90%.
  - Izkata 8y ago
    Your examples are kinda funny, because that could easily be true. Now, if the second one was 90.0% on the other hand...
- taeric 8y ago
  Worse, many people that say "almost always" really just mean "I notice it when it happens, not when it doesn't."
- ska 8y ago
  This is somewhere that common usage and mathematical usage diverge strongly. To anyone versed in measure theory talking about "almost always" wrt probability will mean that there is zero probability of the event not happening (even thought there may be other outcomes in the space).
will_brown 8y ago
When have this type of imprecise (sometimes subjective) verbiage in our legal standards: 1. Beyond a reasonable doubt 2. Perponderance of the evidence (“more likely than not”, which in theory is >50%) 3. Clear and convincing (which is somewhere in between the 2 above)
- occamrazor 8y ago
  There is also a standard terminology for undesirable effects of medications: - Very common: affects more than 1 in 10 people – ie the risk is 10% or higher - Common: affects between 1 in 100 and 1 in 10 people – ie risk is 1% to 10% - Uncommon: affects between 1 in 1,000 and 1 in 100 people – ie risk is 0.1% to 1% - Rare: affects between 1 in 10,000 and 1 in 1,000 people – ie risk is 0.01% to 0.1% -Very rare: affects less than 1 in 10,000 people – ie risk is less than 0.01% (This includes isolated reports)
projectramo 8y ago
Follow up study: when someone says something happens “90% of the time”, how likely do they think it is?
everdev 8y ago
Aren't all adjectives relative and therefore arguable? It's amazing how often they're used in debates or political speech (ex. good, bad, strong, important, dangerous, etc.) when they clearly mean different things to different people, but maybe that's the idea.
- neom 8y ago
  Indeed, this is why the best communicators lean heavily on adverbs and pay careful attention to what adjectives make sense for the audience.
- Senderman 8y ago
  I do think it's the idea, a lot of the time. On the other hand I suspect a lot of people do it without being aware. There's only so much accuracy you can squeeze into a sentence - some people don't notice, some take advantage, some try to teach others to keep an ear out for this exact problem.
kashyapc 8y ago
That impreciseness is one reason why William Zinsser in his book, On Writing Well, argues: - "Get rid of the adjective-by-habit." - "Don't hedge your prose with little timidities. Good writing is lean and confident."
- tgb 8y ago
  Why not just say "with timidities"?
  - kashyapc 8y ago
    I interpreted it ("with little timidities") as a subtle joke.
  - fjsolwmv 8y ago
    "little" calls to mind "litter". One big tinidit in the preface wouldn't be so annoying to read.
- resu_nimda 8y ago
  "Don't hedge your prose with little timidities. Good writing is lean and confident." This is a separate issue, and one I would disagree with. In fact I feel like this is a problematic attitude in our culture. Too many people overconfidently asserting their subjective viewpoints. Real life is full of nuance, gray area, second-guessing, and different perspectives; simple bold assertions usually don't hold water. David Foster Wallace, considered one of the greatest writers of recent times, filled his writings with qualifications, side notes, devil's advocacy, and at times insecure waffling. To me this is a more accurate reflection of the mind and reality and should not be suppressed for a macho bravado façade.
  - 1123581321 8y ago
    Why did you write your opinionated comment in a straightforward manner, then?
    - 8y ago
zaat 8y ago
>When you use a word to describe the likelihood of a probabilistic outcome, you have a lot of wiggle room to make yourself look good after the fact. If a predicted event happens, one might declare: “I told you it would probably happen.” If it doesn’t happen, the fallback might be: “I only said it would probably happen.” The same is true with numbers. If a predicted event happens, one might declare: "I told you there 80 percent that will happen". If it dosen't happen, the fallback might be: "I told you there are 20 percent it will not happen."
crispyambulance 8y ago
It depends on the context. Hillary Clinton had a >70% of winning the US presidential election according to the most responsible analyses (see 538: https://projects.fivethirtyeight.com/2016-election-forecast/ https://projects.fivethirtyeight.com/2016-election-forecast/). Most folks took 70% to mean that she would certainly win and were bitterly disappointed the morning after. On the other hand no sane person would (willingly) play Russian roulette with a 70% or even 5 of 6 chance of "winning". In everyday life, one conflates probability with severity of outcome. This is normal and is part of how people assess and act on risk in a qualitative way.
- lifeisstillgood 8y ago
  That's probably the first time I have mapped Russian Roulette odds to percentages - and 83% chance used to look pretty good. Now I understand Robert Downey Jrs maths skills in Kiss Kiss Bang Bang.
  - sp332 8y ago
    Pascals' Wager: multiply the odds by the cost or benefit of each outcome. The higher the potential cost, the less good your odds look even if the percentage is the same.
    - oculusthrift 8y ago
      Not sure what that has to do with Pascal’s wager? This is just basic “expected value” in probability terms.
      - lifeisstillgood 8y ago
        The cost of "believing" in God, near zero, the expected value if correct - huge :-) Plus wasn't it pascal who invented expected value?
        sp332 8y ago
pacificpendant 8y ago
When people say things like "serious possibility" they are not merely intending to alter the perception of the likelihood but also attempting to impress upon the listener the gravity of the event. In cold war era America would people have felt any different knowing that a Russian invasion was only 20% likely rather than 30%? For something so /serious/ any non-zero probability is something that should be prepared for.
- ScottBurson 8y ago
  Yes, I had the same thought. A "serious possibility" of global thermonuclear war is 1% (maybe smaller). A "serious possibility" of a hangnail is 80%.
jmount 8y ago
Another fun one: Fermi's definition of "remote possibility" as a chance of no more than 1 in 10. (Scary when talking about the odds of initiating a chain reaction, making a small atomic weapon, or even igniting the atmosphere in the first atomic test.) https://books.google.com/books?id=2G2TlJOhGI8C&pg=PA280&lpg=PA280#v=onepage&q&f=false https://books.google.com/books?id=2G2TlJOhGI8C&pg=PA280&lpg=...
- hueving 8y ago
  0 in 10 is still "no more than 1 in 10", so I don't see why that's scary.
  - fjsolwmv 8y ago
    0.9 in 10 is also no more than 1 in 10.
    - hueving 8y ago
      Right, but I'm suggesting that the odds of lighting the atmosphere on fire were calculated to be much lower than 1 in 10, but there just wasn't a 'simple English' category to distinguish them. So I wouldn't get scared until I saw something that suggested it was anywhere near 1 in 10.
dsr_ 8y ago
Related: RFC 2119, https://www.ietf.org/rfc/rfc2119.txt https://www.ietf.org/rfc/rfc2119.txt which defines the key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL". Most subsequent RFCs begin with a reference to it.
GuB-42 8y ago
It also depends on the individual. And as you get to know people better, you tend to interpret their probabilities better. Take the question "are you coming?". "Maybe" can mean "yes, except in case of nuclear war" to "not unless you kidnap me", depending on the person.
cortic 8y ago
Its very likely, that's its not as likely as people likely think it is.
roter 8y ago
For what it is worth, the Intergovernmental Panel on Climate Change uses the following definitions[0]: virtually certain: 99-100% extremely likely: 95-100% very likely: 90-100% likely: 66-100% about as likely as not: 33-66% more likely than not: >50-100% more unlikely than likely: 0-<50% unlikely: 0-33% very unlikely: 0-10% extremely unlikely: 0-5% exceptionally unlikely: 0-1% [0]: https://ipcc.ch/pdf/assessment-report/ar5/syr/AR5_SYR_FINAL_SPM.pdf https://ipcc.ch/pdf/assessment-report/ar5/syr/AR5_SYR_FINAL_...
- s-shellfish 8y ago
  So it follows a normal curve
- deleted 8y ago
  [deleted]
- tinalumfoil 8y ago
  > virtually certain: 99-100% Hopefully whoever wrote that never works in a data center, builds cars, sells insurance, gambles, works on crypto, does scientific computing, or is ever responsible for someone's life.
  - csours 8y ago
    If you do any of those things, you use actual numbers with your words - which, if you actually care about the subject at hand, you should have used numbers in the first place.
  - icedchai 8y ago
    You're not much of a risk taker, are you?
  - throwawaymath 8y ago
    Implicit in your statement is the claim that you cannot acknowledge the existence of a percentile without believing any given feature of your domain can easily satisfy that percentile. That's a non sequitur. The conclusion that follows from that one is also very strange, because it would mean we shouldn't bother quantifying things (or having a name for them) if they can only be expected to happen extremely rarely.
aj7 8y ago
I can summarize the article in a single sentence. “Something is likely” has a huge variance.
anuj_nm 8y ago
This makes me thankful for Amazon's document-writing culture. Ambiguous words like very/could/should/few/large are avoided or at least qualified with a range. This helps us avoid ambiguity, regardless of the amount of context a reader has.
sanbor 8y ago
In my experience, putting numbers to your gut feeling probabilities causes people to not take them seriously. Example: "I think there is 30% chances that I will get a promotion next month". If I say 30% people ask how I came up with that number. If I say "not very likely" then it gets accepted as an educated guess. Probably because we're used that those numbers must come from some dataset. Or should I say "I think there is a chance of 40% that things are like that because we're used that those numbers must come from some dataset".
- a13n 8y ago
  30% is specific, as if it's the result of a calculation in a spreadsheet. But with something like getting a promotion, how would you calculate that so specifically? You can't. That's why people don't take it seriously. "Not very likely" is a rough estimate, like "probably not", or "less than 30% likely". It's a lot more believable that with the information you know, you're able to predict with that certainty.
safgasCVS 8y ago
"Lesson 1: Use probabilities instead of words to avoid misinterpretation." Probabilities are meaningless unless it’s a repeatable experiment otherwise its a ludic fallacy eg "There's a 70% chance of Hillary winning". This is an un-provable statement. Either she wins and prediction was right, or she loses and it counts as part of the 30%. This is Nate Silver's get-out-of-jail-free card so even when he's wrong he comes off as being right. i.e. this statement makes sense in a casino and nowhere else. "Lesson 2: Use structured approaches to set probabilities." Probabilities are meaningless by themselves. Path dependency matters a great deal to actual humans but not to business professors. A strategy that works well for the ensemble wont necessarily work well for the individual. e.g. if you save for retirement for the average life expectancy then 50% of the people would be screwed and 50% of the people would have saved too much. i.e. The cost of being right/wrong is what matters and not the probability.
- fjsolwmv 8y ago
  Nate silver makes hundreds of predictions every year. You can compute his average and error in his estimates.
- archgoon 8y ago
  > Probabilities are meaningless unless it’s a repeatable experiment otherwise its a ludic fallacy Um... this goes against the entirety of the Bayesian approach to statistics. I think you'd find a lot of very intelligent people who disagree strongly with this statement. The Bayesian approach takes probabilities as subjective confidences. You can describe confidences as "well calibrated" if, when you look at their historical guesses, if their 70% assessments are correct 70% of the time.
  - safgasCVS 8y ago
    ". I think you'd find a lot of very intelligent people who disagree strongly with this statement. " I never claimed to be intelligent. " You can describe confidences as "well calibrated" if, when you look at their historical guesses, if their 70% assessments are correct 70% of the time." - Again, if you're trying to figure out if a coin is split 50/50 then yes, but without being able to repeat the same experiment you're fooling yourself and the whole aspect of bayesian thinking I think goes out the window. eg me being right about unrelated topics doesn't mean I'm right/wrong about specific topics.
musage 8y ago
Depending on context, I just might ignore it as the padding it is. Same with the negative "I'm not entirely sure X is true" which is either becoming more common, or which I notice more and more. Hiding goal posts in a swamp is worse than moving them.
jcrites 8y ago
This article, and some of the comments here, reminded me of another article (and GDC talk) by Civilization game designer Sid Meier, about his experience with players' perception of probability in games. Sid's talk grapples with the issue "If the game says you have 3-to-1 odds to win a battle, how often do players actually expect to win?" > When designing the combat system in Civilization: Revolution, Sid Meier found himself up against some interesting design problems. His players didn't understand math. In Civ Rev, the strength of units were displayed up front to players before battle to show the odds of victory. For example, an attacking unit might be rated at 1.5 with the defending unit at 0.5. This is a 3-to-1 situation. > Unfortunately, the testers expected to win this battle every time despite there being a 25% chance of losing each time. Sid tweaked the math to make the player win more in this situation. Next, the reverse case was tested. The player had 1-to-3 odds. If they won, the math was functioning properly. They had a slim chance to win and they did. > Sid identified a few cases of interest. When the player was presented with 3-to-1 or 4-to-1 odds, they expect to win. With 2-to-1 odds, the player will accept losing some of the time, but expect to win at 20-to-10, which is just a larger expression of 2-to-1. When the numbers get larger, the perceived advantage grows. http://www.shacknews.com/article/62807/sid-meier-and-rob-pardo http://www.shacknews.com/article/62807/sid-meier-and-rob-par... Here is a link to the actual GDC talk by Sid with the content about probability: https://youtu.be/bY7aRJE-oOY?t=18m22s https://youtu.be/bY7aRJE-oOY?t=18m22s (It's true. When playing a Civ game, it's not fun to have a 10-to-1 strength advantage and lose the battle anyway.) In later games, Sid removed probability from the game in favor of an outcome that's predictable. Instead, each unit will be damaged in proportion to the ratio of the units' strengths (or something like that).
- throwaway37585 8y ago
  Maybe the key here is that strength ratio != odds, under most intuitive definitions of strength. If someone is twice as strong as you, they're arguably much more than twice as likely to defeat you. If someone has twice the number of units as you, they're also more than twice as likely to defeat you.
any1 8y ago
I usually just let the branch predictor figure it out on its own.
etqwzutewzu 8y ago
likely
deleted 8y ago
[deleted]
BrandoElFollito 8y ago
I work in security and I am asked all the time about the likelihood of horrible things which may happen. I cannot, ever, give a percentage ("70% chance we will get hacked if this and that"). I either say that I do it know and nobody will, or use "probably" or "unlikely". These are wide, hand waving categories. I do that not because I do not want to be wrong but just because I have only a vague idea, classified into "maybe" and "maybe not"
Chronos309 8y ago
I PERSONALLY decided if it seems like 20-25% probability, this is 'likely' because it means I can accomplish it if I can try 4-5 times. If it is 1%, I'd have to attempt 100 times to make a thing happen.

131 points by randomwalker 8y ago

Using numbers for probabilities is not a panacea either, when those numbers are not the result of a calculation. One person might say "99% of the time" to mean "almost always", and another person might say "9 out of 10 times" to mean exactly the same thing. The problem is that it's hard to estimate the probability of something that you know happens "almost always" without doing the counting, which most people don't do. And hence it's difficult to gain an intuition for what 99% means exactly. Furthermore, there is also the possibility that two people share the same intuition about a given word/phrase, but then disagree about which number describes that intuition. This could account for part of the results of this paper.

c3534l 8y ago
A good example of this is ratings on Amazon. You can give up to five stars, but most people just give 1 or 5 depending on if they were satisfied or dissatisfied. Additionally, people confuse precision for certainty and will perceive an estimate of 89.1% as more accurate than 90%.
- Izkata 8y ago
  Your examples are kinda funny, because that could easily be true. Now, if the second one was 90.0% on the other hand...
taeric 8y ago
Worse, many people that say "almost always" really just mean "I notice it when it happens, not when it doesn't."
ska 8y ago
This is somewhere that common usage and mathematical usage diverge strongly. To anyone versed in measure theory talking about "almost always" wrt probability will mean that there is zero probability of the event not happening (even thought there may be other outcomes in the space).

will_brown 8y ago

When have this type of imprecise (sometimes subjective) verbiage in our legal standards: 1. Beyond a reasonable doubt 2. Perponderance of the evidence (“more likely than not”, which in theory is >50%) 3. Clear and convincing (which is somewhere in between the 2 above)

occamrazor 8y ago
There is also a standard terminology for undesirable effects of medications: - Very common: affects more than 1 in 10 people – ie the risk is 10% or higher - Common: affects between 1 in 100 and 1 in 10 people – ie risk is 1% to 10% - Uncommon: affects between 1 in 1,000 and 1 in 100 people – ie risk is 0.1% to 1% - Rare: affects between 1 in 10,000 and 1 in 1,000 people – ie risk is 0.01% to 0.1% -Very rare: affects less than 1 in 10,000 people – ie risk is less than 0.01% (This includes isolated reports)

projectramo 8y ago

Follow up study: when someone says something happens “90% of the time”, how likely do they think it is?

everdev 8y ago

Aren't all adjectives relative and therefore arguable? It's amazing how often they're used in debates or political speech (ex. good, bad, strong, important, dangerous, etc.) when they clearly mean different things to different people, but maybe that's the idea.

neom 8y ago
Indeed, this is why the best communicators lean heavily on adverbs and pay careful attention to what adjectives make sense for the audience.
Senderman 8y ago
I do think it's the idea, a lot of the time. On the other hand I suspect a lot of people do it without being aware. There's only so much accuracy you can squeeze into a sentence - some people don't notice, some take advantage, some try to teach others to keep an ear out for this exact problem.

kashyapc 8y ago

That impreciseness is one reason why William Zinsser in his book, On Writing Well, argues: - "Get rid of the adjective-by-habit." - "Don't hedge your prose with little timidities. Good writing is lean and confident."

tgb 8y ago
Why not just say "with timidities"?
- kashyapc 8y ago
  I interpreted it ("with little timidities") as a subtle joke.
- fjsolwmv 8y ago
  "little" calls to mind "litter". One big tinidit in the preface wouldn't be so annoying to read.
resu_nimda 8y ago
"Don't hedge your prose with little timidities. Good writing is lean and confident." This is a separate issue, and one I would disagree with. In fact I feel like this is a problematic attitude in our culture. Too many people overconfidently asserting their subjective viewpoints. Real life is full of nuance, gray area, second-guessing, and different perspectives; simple bold assertions usually don't hold water. David Foster Wallace, considered one of the greatest writers of recent times, filled his writings with qualifications, side notes, devil's advocacy, and at times insecure waffling. To me this is a more accurate reflection of the mind and reality and should not be suppressed for a macho bravado façade.
- 1123581321 8y ago
  Why did you write your opinionated comment in a straightforward manner, then?
  - 8y ago

zaat 8y ago

>When you use a word to describe the likelihood of a probabilistic outcome, you have a lot of wiggle room to make yourself look good after the fact. If a predicted event happens, one might declare: “I told you it would probably happen.” If it doesn’t happen, the fallback might be: “I only said it would probably happen.” The same is true with numbers. If a predicted event happens, one might declare: "I told you there 80 percent that will happen". If it dosen't happen, the fallback might be: "I told you there are 20 percent it will not happen."

crispyambulance 8y ago

It depends on the context. Hillary Clinton had a >70% of winning the US presidential election according to the most responsible analyses (see 538: https://projects.fivethirtyeight.com/2016-election-forecast/ https://projects.fivethirtyeight.com/2016-election-forecast/). Most folks took 70% to mean that she would certainly win and were bitterly disappointed the morning after. On the other hand no sane person would (willingly) play Russian roulette with a 70% or even 5 of 6 chance of "winning". In everyday life, one conflates probability with severity of outcome. This is normal and is part of how people assess and act on risk in a qualitative way.

lifeisstillgood 8y ago
That's probably the first time I have mapped Russian Roulette odds to percentages - and 83% chance used to look pretty good. Now I understand Robert Downey Jrs maths skills in Kiss Kiss Bang Bang.
- sp332 8y ago
  Pascals' Wager: multiply the odds by the cost or benefit of each outcome. The higher the potential cost, the less good your odds look even if the percentage is the same.
  - oculusthrift 8y ago
    Not sure what that has to do with Pascal’s wager? This is just basic “expected value” in probability terms.
    - lifeisstillgood 8y ago
      The cost of "believing" in God, near zero, the expected value if correct - huge :-) Plus wasn't it pascal who invented expected value?
      - sp332 8y ago

pacificpendant 8y ago

When people say things like "serious possibility" they are not merely intending to alter the perception of the likelihood but also attempting to impress upon the listener the gravity of the event. In cold war era America would people have felt any different knowing that a Russian invasion was only 20% likely rather than 30%? For something so /serious/ any non-zero probability is something that should be prepared for.

ScottBurson 8y ago
Yes, I had the same thought. A "serious possibility" of global thermonuclear war is 1% (maybe smaller). A "serious possibility" of a hangnail is 80%.

jmount 8y ago

Another fun one: Fermi's definition of "remote possibility" as a chance of no more than 1 in 10. (Scary when talking about the odds of initiating a chain reaction, making a small atomic weapon, or even igniting the atmosphere in the first atomic test.) https://books.google.com/books?id=2G2TlJOhGI8C&pg=PA280&lpg=PA280#v=onepage&q&f=false https://books.google.com/books?id=2G2TlJOhGI8C&pg=PA280&lpg=...

hueving 8y ago
0 in 10 is still "no more than 1 in 10", so I don't see why that's scary.
- fjsolwmv 8y ago
  0.9 in 10 is also no more than 1 in 10.
  - hueving 8y ago
    Right, but I'm suggesting that the odds of lighting the atmosphere on fire were calculated to be much lower than 1 in 10, but there just wasn't a 'simple English' category to distinguish them. So I wouldn't get scared until I saw something that suggested it was anywhere near 1 in 10.

dsr_ 8y ago

Related: RFC 2119, https://www.ietf.org/rfc/rfc2119.txt https://www.ietf.org/rfc/rfc2119.txt which defines the key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL". Most subsequent RFCs begin with a reference to it.

GuB-42 8y ago

It also depends on the individual. And as you get to know people better, you tend to interpret their probabilities better. Take the question "are you coming?". "Maybe" can mean "yes, except in case of nuclear war" to "not unless you kidnap me", depending on the person.

cortic 8y ago

Its very likely, that's its not as likely as people likely think it is.

roter 8y ago

For what it is worth, the Intergovernmental Panel on Climate Change uses the following definitions[0]: virtually certain: 99-100% extremely likely: 95-100% very likely: 90-100% likely: 66-100% about as likely as not: 33-66% more likely than not: >50-100% more unlikely than likely: 0-<50% unlikely: 0-33% very unlikely: 0-10% extremely unlikely: 0-5% exceptionally unlikely: 0-1% [0]: https://ipcc.ch/pdf/assessment-report/ar5/syr/AR5_SYR_FINAL_SPM.pdf https://ipcc.ch/pdf/assessment-report/ar5/syr/AR5_SYR_FINAL_...

s-shellfish 8y ago
So it follows a normal curve
deleted 8y ago
[deleted]
tinalumfoil 8y ago
> virtually certain: 99-100% Hopefully whoever wrote that never works in a data center, builds cars, sells insurance, gambles, works on crypto, does scientific computing, or is ever responsible for someone's life.
- csours 8y ago
  If you do any of those things, you use actual numbers with your words - which, if you actually care about the subject at hand, you should have used numbers in the first place.
- icedchai 8y ago
  You're not much of a risk taker, are you?
- throwawaymath 8y ago
  Implicit in your statement is the claim that you cannot acknowledge the existence of a percentile without believing any given feature of your domain can easily satisfy that percentile. That's a non sequitur. The conclusion that follows from that one is also very strange, because it would mean we shouldn't bother quantifying things (or having a name for them) if they can only be expected to happen extremely rarely.

aj7 8y ago

I can summarize the article in a single sentence. “Something is likely” has a huge variance.

anuj_nm 8y ago

This makes me thankful for Amazon's document-writing culture. Ambiguous words like very/could/should/few/large are avoided or at least qualified with a range. This helps us avoid ambiguity, regardless of the amount of context a reader has.

sanbor 8y ago

In my experience, putting numbers to your gut feeling probabilities causes people to not take them seriously. Example: "I think there is 30% chances that I will get a promotion next month". If I say 30% people ask how I came up with that number. If I say "not very likely" then it gets accepted as an educated guess. Probably because we're used that those numbers must come from some dataset. Or should I say "I think there is a chance of 40% that things are like that because we're used that those numbers must come from some dataset".

a13n 8y ago
30% is specific, as if it's the result of a calculation in a spreadsheet. But with something like getting a promotion, how would you calculate that so specifically? You can't. That's why people don't take it seriously. "Not very likely" is a rough estimate, like "probably not", or "less than 30% likely". It's a lot more believable that with the information you know, you're able to predict with that certainty.

safgasCVS 8y ago

"Lesson 1: Use probabilities instead of words to avoid misinterpretation." Probabilities are meaningless unless it’s a repeatable experiment otherwise its a ludic fallacy eg "There's a 70% chance of Hillary winning". This is an un-provable statement. Either she wins and prediction was right, or she loses and it counts as part of the 30%. This is Nate Silver's get-out-of-jail-free card so even when he's wrong he comes off as being right. i.e. this statement makes sense in a casino and nowhere else. "Lesson 2: Use structured approaches to set probabilities." Probabilities are meaningless by themselves. Path dependency matters a great deal to actual humans but not to business professors. A strategy that works well for the ensemble wont necessarily work well for the individual. e.g. if you save for retirement for the average life expectancy then 50% of the people would be screwed and 50% of the people would have saved too much. i.e. The cost of being right/wrong is what matters and not the probability.

fjsolwmv 8y ago
Nate silver makes hundreds of predictions every year. You can compute his average and error in his estimates.
archgoon 8y ago
> Probabilities are meaningless unless it’s a repeatable experiment otherwise its a ludic fallacy Um... this goes against the entirety of the Bayesian approach to statistics. I think you'd find a lot of very intelligent people who disagree strongly with this statement. The Bayesian approach takes probabilities as subjective confidences. You can describe confidences as "well calibrated" if, when you look at their historical guesses, if their 70% assessments are correct 70% of the time.
- safgasCVS 8y ago
  ". I think you'd find a lot of very intelligent people who disagree strongly with this statement. " I never claimed to be intelligent. " You can describe confidences as "well calibrated" if, when you look at their historical guesses, if their 70% assessments are correct 70% of the time." - Again, if you're trying to figure out if a coin is split 50/50 then yes, but without being able to repeat the same experiment you're fooling yourself and the whole aspect of bayesian thinking I think goes out the window. eg me being right about unrelated topics doesn't mean I'm right/wrong about specific topics.

musage 8y ago

Depending on context, I just might ignore it as the padding it is. Same with the negative "I'm not entirely sure X is true" which is either becoming more common, or which I notice more and more. Hiding goal posts in a swamp is worse than moving them.

jcrites 8y ago

This article, and some of the comments here, reminded me of another article (and GDC talk) by Civilization game designer Sid Meier, about his experience with players' perception of probability in games. Sid's talk grapples with the issue "If the game says you have 3-to-1 odds to win a battle, how often do players actually expect to win?" > When designing the combat system in Civilization: Revolution, Sid Meier found himself up against some interesting design problems. His players didn't understand math. In Civ Rev, the strength of units were displayed up front to players before battle to show the odds of victory. For example, an attacking unit might be rated at 1.5 with the defending unit at 0.5. This is a 3-to-1 situation. > Unfortunately, the testers expected to win this battle every time despite there being a 25% chance of losing each time. Sid tweaked the math to make the player win more in this situation. Next, the reverse case was tested. The player had 1-to-3 odds. If they won, the math was functioning properly. They had a slim chance to win and they did. > Sid identified a few cases of interest. When the player was presented with 3-to-1 or 4-to-1 odds, they expect to win. With 2-to-1 odds, the player will accept losing some of the time, but expect to win at 20-to-10, which is just a larger expression of 2-to-1. When the numbers get larger, the perceived advantage grows. http://www.shacknews.com/article/62807/sid-meier-and-rob-pardo http://www.shacknews.com/article/62807/sid-meier-and-rob-par... Here is a link to the actual GDC talk by Sid with the content about probability: https://youtu.be/bY7aRJE-oOY?t=18m22s https://youtu.be/bY7aRJE-oOY?t=18m22s (It's true. When playing a Civ game, it's not fun to have a 10-to-1 strength advantage and lose the battle anyway.) In later games, Sid removed probability from the game in favor of an outcome that's predictable. Instead, each unit will be damaged in proportion to the ratio of the units' strengths (or something like that).

throwaway37585 8y ago
Maybe the key here is that strength ratio != odds, under most intuitive definitions of strength. If someone is twice as strong as you, they're arguably much more than twice as likely to defeat you. If someone has twice the number of units as you, they're also more than twice as likely to defeat you.

any1 8y ago

I usually just let the branch predictor figure it out on its own.

etqwzutewzu 8y ago

likely

deleted 8y ago

[deleted]

BrandoElFollito 8y ago

I work in security and I am asked all the time about the likelihood of horrible things which may happen. I cannot, ever, give a percentage ("70% chance we will get hacked if this and that"). I either say that I do it know and nobody will, or use "probably" or "unlikely". These are wide, hand waving categories. I do that not because I do not want to be wrong but just because I have only a vague idea, classified into "maybe" and "maybe not"

Chronos309 8y ago

I PERSONALLY decided if it seems like 20-25% probability, this is 'likely' because it means I can accomplish it if I can try 4-5 times. If it is 1%, I'd have to attempt 100 times to make a thing happen.