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Author Topic:   The Nature of Scepticism
ringo
Member (Idle past 411 days)
Posts: 20940
From: frozen wasteland
Joined: 03-23-2005


(1)
Message 241 of 271 (717100)
01-24-2014 10:45 AM
Reply to: Message 220 by Modulous
01-23-2014 1:29 PM


Re: mad genius
Modulous writes:
Therefore - would it not be true that multiple false positives actually do effect the probability that the next alarm will be correct?
The numeric value of the probability is irrelevant. What matters is the risk of being wrong. The boy-who-cried-wolf story is about resource management. Can we afford not to prepare for a real wolf?

This message is a reply to:
 Message 220 by Modulous, posted 01-23-2014 1:29 PM Modulous has replied

Replies to this message:
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Stile
Member
Posts: 4295
From: Ontario, Canada
Joined: 12-02-2004


Message 242 of 271 (717109)
01-24-2014 11:34 AM
Reply to: Message 240 by ringo
01-24-2014 10:41 AM


Re: Change of Pace
ringo writes:
The villagers' "objective" conclusion is based on an inadequate subset of the available evidence. They're ignoring the fact that wolves exist.
I never really liked the story either.
That's why I didn't include the entire story in my example.
I'm making an example in order to simplify things, not complicate them.
Bringing the example into the present day, suppose the boy pulls a fire alarm. The firefighters arrive and there's no fire. The boy pulls the alarm again and again the firefighters find no fire. This goes on and on but the firefighters keep coming - because they've drawn an actual objective conclusion that there could be a fire.
I agree.
The fable and the lesson are kind of silly, as is the example you show here.
That's why I simplified the scenario... to take something familiar and delve into some basic aspects.
Sorry for any confusion.
My issue is that the villagers conclusion is not really objective.
Okay. I agree that Aesop was not a scientist? I'm not trying to discuss what the villagers did, or even should do, at all.

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New Cat's Eye
Inactive Member


Message 243 of 271 (717115)
01-24-2014 12:07 PM
Reply to: Message 241 by ringo
01-24-2014 10:45 AM


Re: mad genius
The numeric value of the probability is irrelevant. What matters is the risk of being wrong.
Yeah, sometimes our water pressure drops here at work, and that causes the fire alarm to go off. We have lots of false positives, but we all still grudgingly evacuate the building every time it goes off, even though we're all pretty sure there is no fire.

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AZPaul3
Member
Posts: 8513
From: Phoenix
Joined: 11-06-2006
Member Rating: 5.2


Message 244 of 271 (717116)
01-24-2014 12:14 PM
Reply to: Message 238 by Modulous
01-24-2014 7:25 AM


Re: The 6 Is Up.
Conditional probabilities, sir. If the dice reader says it is a six then what is the probability that the dice rolled a six?
If your reader is always faithful and is displaying 6 then the outcome of the 1-6 probability came in as a 6
If I told you that my dice reader is designed to never display the correct result ...
If your device is a faithful liar then when it says 6 you are assured the roll was not 6. But the roll itself was a 1-6 chance. If the roll landed on 6 then your faithful liar would display a different number.
Your wolf detector has only a 1/365 chance of being right each - and - every - day, regardless of how many times you try.
Exactly. Where did this number come from? Did you derive this number from the number of false positives?
The 1/365 accuracy rate is indeed established by the number of false positives experienced. Once established that rate, unless you change the detector, remains. I agree.
If so, then you agree that the number of false positives do effect the probability that the next alarm will be correct.
There appears to be a vernacular problem here. I'm thinking you are looking at one situation and I am seeing another.
Are you saying that after 19 days of false positives you can tentatively say the next day has a 1-20 probability of being right? Then at 39 days of constant false positives you are now saying that the next day has a 1-40 chance of being correct?
If so then this is all basakwards. You cannot say anything about the probabilities until you hit on a true positive.
I will grant you that on the 39th day you can say that the next day has "at least a 1-40 chance" with the caveat that it may be considerably more than 1-40 and is thus unknown. You have only placed a lower bound.
But can you not see that as the number of false reports goes up, our confidence in the reports goes down?
Well, duh.
Is this too pedantic?

This message is a reply to:
 Message 238 by Modulous, posted 01-24-2014 7:25 AM Modulous has replied

Replies to this message:
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Modulous
Member
Posts: 7801
From: Manchester, UK
Joined: 05-01-2005


Message 245 of 271 (717129)
01-24-2014 2:11 PM
Reply to: Message 244 by AZPaul3
01-24-2014 12:14 PM


Re: The 6 Is Up.
But can you not see that as the number of false reports goes up, our confidence in the reports goes down?
Well, duh.
Is this too pedantic?
So now are you agreeing with the statement 'multiple false positives actually do effect the probability that the next alarm will be correct'?

This message is a reply to:
 Message 244 by AZPaul3, posted 01-24-2014 12:14 PM AZPaul3 has replied

Replies to this message:
 Message 247 by AZPaul3, posted 01-24-2014 2:49 PM Modulous has replied

  
Modulous
Member
Posts: 7801
From: Manchester, UK
Joined: 05-01-2005


Message 246 of 271 (717131)
01-24-2014 2:13 PM
Reply to: Message 241 by ringo
01-24-2014 10:45 AM


Re: mad genius
The numeric value of the probability is irrelevant. What matters is the risk of being wrong. The boy-who-cried-wolf story is about resource management. Can we afford not to prepare for a real wolf?
Largely what I said in Message 236, right?

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AZPaul3
Member
Posts: 8513
From: Phoenix
Joined: 11-06-2006
Member Rating: 5.2


Message 247 of 271 (717136)
01-24-2014 2:49 PM
Reply to: Message 245 by Modulous
01-24-2014 2:11 PM


Re: The 6 Is Up.
So now are you agreeing with the statement 'multiple false positives actually do effect the probability that the next alarm will be correct'?
At what point? When testing to see how reliable the thing is or once the baseline has been established by having hit a true positive?

This message is a reply to:
 Message 245 by Modulous, posted 01-24-2014 2:11 PM Modulous has replied

Replies to this message:
 Message 248 by Modulous, posted 01-24-2014 2:57 PM AZPaul3 has replied

  
Modulous
Member
Posts: 7801
From: Manchester, UK
Joined: 05-01-2005


Message 248 of 271 (717139)
01-24-2014 2:57 PM
Reply to: Message 247 by AZPaul3
01-24-2014 2:49 PM


Re: The 6 Is Up.
At what point?
I don't see the need to privilege any particular point.
When testing to see how reliable the thing is or once the baseline has been established by having hit a true positive?
In order to have confidence in the true ratio of true to false positives, we'd need several true positives. But if you set a fire alarm in your house that goes off every 10 seconds, you don't need to wait for the day an actual fire occurs to conclude the fire alarm is unreliable and gives off too many false positives. And it would still be the case that an alarm that gives a false positive every 10 seconds is worse than an alarm that gives a false positive every six months.

This message is a reply to:
 Message 247 by AZPaul3, posted 01-24-2014 2:49 PM AZPaul3 has replied

Replies to this message:
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AZPaul3
Member
Posts: 8513
From: Phoenix
Joined: 11-06-2006
Member Rating: 5.2


Message 249 of 271 (717156)
01-24-2014 4:20 PM
Reply to: Message 248 by Modulous
01-24-2014 2:57 PM


Re: The 6 Is Up.
Agreed. Sorry to have taken your time away from the real issue here. Later.

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RAZD
Member (Idle past 1404 days)
Posts: 20714
From: the other end of the sidewalk
Joined: 03-14-2004


Message 250 of 271 (717418)
01-27-2014 10:22 AM
Reply to: Message 229 by 1.61803
01-23-2014 5:11 PM


Re: Change of Pace
His brother ASSUMED it was a robber and CONCLUDED he was a threat.
Sad.
However it is not without flaws. Which is why it is sometimes prudent to error on the side of safety. If one assumes there is always a wolf one will never be surprised when the wolf does come for the herd.
Indeed. That was the error the villagers made. If they had been skeptical of their conclusion that should have lead to a different approach.

we are limited in our ability to understand
by our ability to understand
Rebel American Zen Deist
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to share.


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RAZD
Member (Idle past 1404 days)
Posts: 20714
From: the other end of the sidewalk
Joined: 03-14-2004


Message 251 of 271 (717424)
01-27-2014 10:45 AM
Reply to: Message 235 by Modulous
01-23-2014 6:49 PM


Re: the point - a consistent skeptical approach
Then they made a mistake to let him do it again.
Indeed, you might say nobody believes a liar...even when he is telling the truth
Or you might say the person was unreliable to provide objective evidence to whether or not a wolf was actually around. Next time could be 'true' next time could be 'false' (or not validated), and you could also have a false positive or a false negative.
The point is how a consistent skeptical approach would come to the best solution yes?
Yes. So what is the best solution based on your skeptical approach? Give me a few seconds, I'll reveal a simple model in my next post.
The past evidence of wolves means one cannot conclude that they are not a threat (the probability of a wolf attack is non-zero).
Because the sheep are valuable a more reliable lookout system is needed than one of questionable value - ∴ replace with or add a different person (increase the probability of an accurate report).
skeptical of the ability of the boy to provide an accurate report
skeptical of the conclusion that the boy provides false witness

we are limited in our ability to understand
by our ability to understand
Rebel American Zen Deist
... to learn ... to think ... to live ... to laugh ...
to share.


Join the effort to solve medical problems, AIDS/HIV, Cancer and more with Team EvC! (click)

This message is a reply to:
 Message 235 by Modulous, posted 01-23-2014 6:49 PM Modulous has replied

Replies to this message:
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RAZD
Member (Idle past 1404 days)
Posts: 20714
From: the other end of the sidewalk
Joined: 03-14-2004


Message 252 of 271 (717431)
01-27-2014 11:24 AM
Reply to: Message 239 by Stile
01-24-2014 10:19 AM


wolf wolf wolf
If we personally decide that there is "insufficient evidence" it doesn't mean that what evidence is there no longer exists... it doesn't mean that an objective, evidence-based conclusion cannot be made... it just means that we do not have confidence in that conclusion.
Because it is based on opinion/bias/belief ... particularly the assumption that the evidence you have is indicative of reality. The evidence is neither corroborated nor invalidated.
And even if boy may have cried wolf when there was no wolf, you don't have evidence that the next time will be the same.
Absolutely true.
Conclusions based on objective evidence do not make predictions of the future.
People make predictions of the future.
Based on opinion/bias/belief ... and a failure to be skeptical of that conclusion if acted upon.
I'm just trying to show you that objective evidence does still exist, and it's possible that we may personally judge this objective evidence to "not be enough" for us to follow your chart to path B, C or D.
Curiously I never said that evidence was non-existent, just that it was not sufficient to form a valid conclusion. One person sighting a wolf in the woods is not sufficient evidence for people to conclude that they are a real threat or that they are not a real threat when nobody else sees it. In this case a decision is necessary to provide adequate protection for the sheep, and several possibilities are available:
  1. guess that wolves are not around and that the boy will be reliable next time
  2. guess that wolves are around and that the boy will be reliable next time
  3. guess that wolves are not around and that the boy will not be reliable next time
  4. guess that the wolves are around and that the boy will not be reliable next time
  5. conclude that more information needs to be obtained before more reliable guesses could be made and that you have time and means to do this
  6. conclude that more information needs to be obtained before more reliable guesses could be made and that you do not have time to do this
Positions a, b, and c would not present a problem, but d would open the possibility of a wolf attack on the sheep occurring, and this would be an undesirable result.
Position d means that false positives (c) are possible while waiting for more information but assuming that false negatives (d) do not occur, and that it is okay to climb the mountain for each false or possibly true positive in order to protect the sheep.
Position e means thoroughly looking around for wolves within the possible (large) range of wolves. It is reasonable to investigate further due to the potential danger to the sheep.
Position f means adding or replacing observers to watch for wolves in order to see if the sighting is replicated while increasing the protection of the sheep due to the potential danger.
A cost benefit analysis would likely result in position f being followed.

we are limited in our ability to understand
by our ability to understand
Rebel American Zen Deist
... to learn ... to think ... to live ... to laugh ...
to share.


Join the effort to solve medical problems, AIDS/HIV, Cancer and more with Team EvC! (click)

This message is a reply to:
 Message 239 by Stile, posted 01-24-2014 10:19 AM Stile has replied

Replies to this message:
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Modulous
Member
Posts: 7801
From: Manchester, UK
Joined: 05-01-2005


Message 253 of 271 (717433)
01-27-2014 11:32 AM
Reply to: Message 251 by RAZD
01-27-2014 10:45 AM


Re: the point - a consistent skeptical approach
Because the sheep are valuable a more reliable lookout system is needed than one of questionable value - ∴ replace with or add a different person (increase the probability of an accurate report).
And if a replacement was not possible at the time? Should we always go on wolf alert when the boy cries an alarm, or does there come a time when we should just ignore the boy until such time as a replacement can be arranged?
skeptical of the conclusion that the boy provides false witness
What evidence would cause you to change your mind, to cease being sceptical of this conclusion?

This message is a reply to:
 Message 251 by RAZD, posted 01-27-2014 10:45 AM RAZD has replied

Replies to this message:
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RAZD
Member (Idle past 1404 days)
Posts: 20714
From: the other end of the sidewalk
Joined: 03-14-2004


Message 254 of 271 (717436)
01-27-2014 11:45 AM
Reply to: Message 253 by Modulous
01-27-2014 11:32 AM


Re: the point - a consistent skeptical approach
What evidence would cause you to change your mind, to cease being sceptical of this conclusion?
Admission of lying, independent observed real-time invalidation.
And if a replacement was not possible at the time? Should we always go on wolf alert when the boy cries an alarm, or does there come a time when we should just ignore the boy until such time as a replacement can be arranged?
Yes, or you might as well not have anyone there. Or you conclude that you don't need those sheep? or that the number that might be taken is an acceptable risk? In which case you don't need anyone there?

we are limited in our ability to understand
by our ability to understand
Rebel American Zen Deist
... to learn ... to think ... to live ... to laugh ...
to share.


Join the effort to solve medical problems, AIDS/HIV, Cancer and more with Team EvC! (click)

This message is a reply to:
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Stile
Member
Posts: 4295
From: Ontario, Canada
Joined: 12-02-2004


Message 255 of 271 (717446)
01-27-2014 2:30 PM
Reply to: Message 252 by RAZD
01-27-2014 11:24 AM


"Wrong" does not equal "opinion"
RAZD writes:
Because it is based on opinion/bias/belief ... particularly the assumption that the evidence you have is indicative of reality. The evidence is neither corroborated nor invalidated.
This is the issue. This statement can be taken 2 different ways, and they're both wrong.
1. "The evidence being indicative of reality" could be taken to reference the past observation. The objective statement itself:
The boy cries wolf... the village expert wolf-hunters checked and concluded that there was no wolf.
Then it's incorrect. This evidence is corroborated and validated... that's what the village experts are for... to corroborate and validate the observation that there is no wolf.
Therefore, we have objective, verified information that when the boy cried wolf, there was no wolf (for this one observation, in the past).
2. "The evidence being indicative of reality" could be taken to reference the future observation. The objective conclusion: that based upon this single observation... when the boy cries wolf again, then there will be no wolf at that time.
This is, strictly, correct (that this evidence is not indicative of reality). However, it's like trying to show the best path up a mountain and claiming "you have to increase your elevation."
No amount of repeated observations can make this "indicative of reality" That's the point, even after many objective, verified observations that the boy cried wolf... the village expert wolf-hunters check and conclude that there was no wolf.... do it 100,000 times in a row. It is still "not indicative of reality" that when the boy cries wolf the next time, then there will be no wolf at that time.
There is no such thing as an objective conclusion or theory that is "indicative of reality" for future observations. The only thing that is "indicative of reality" is past observations.
Objective conclusions do not make future predictions that are "indicative of reality." The observations don't know the future any more than you do. They only make future predictions that reflect our objective observations from the past.
So, what is it?
  • Are you referencing the past observation here? And then you're incorrect because the information actually is objective and "indicative of reality" because the evidence has been verified, corroborated and validated by the expert wolf hunters?
  • Are you referencing the future observation here? And then you're incorrect because no one is ever claiming that the objective information is actually indicative of a future observation. This just isn't how science works.
Later in your recent message, you say something else:
One person sighting a wolf in the woods is not sufficient evidence for people to conclude that they are a real threat or that they are not a real threat when nobody else sees it.
This is something we agree on.
However, if we did conclude that when the boy cries wolf again, then there will be no wolf... this is not "based on opinion/bias/belief."
It is based on objective evidence... the one observation.
It's highly likely to be wrong... and there's a very low level of confidence in the conclusion.
But it's absolutely wrong to say it's "based on opionion/bias belief" because it's not. It's based on the one objective, verified observation.
This makes it an objective conclusion.
Not a very confident (good) one... but one all the same.
Edited by Stile, : Just some minor clarity.

This message is a reply to:
 Message 252 by RAZD, posted 01-27-2014 11:24 AM RAZD has replied

Replies to this message:
 Message 256 by RAZD, posted 01-27-2014 5:39 PM Stile has replied
 Message 257 by New Cat's Eye, posted 01-28-2014 10:10 AM Stile has replied

  
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