What Is The Statistical Probability That All Sightings Are False?

[Guest FuriousGeorge]

Yep. As do people who are neither. Who's right? Until we all can agree upon the variables, there will be different answers. I believe the goal of the OP was to find one.

[Guest Jodie]

Well Parn, I would say any individual report has a 50/50 chance of being false.

[Guest Loonsquatch]

This has always been the most compelling part of this discussion to me. How could so many many people, with so much to lose for telling anyone about their sighting be 100% wrong? The PGF is what it is, but the "attitudes" of those who claim to have actually seen this animal are just too much for me to discount as being a mistake or a hoax. Why do I say that? Well, despite not believing in ESP, or any psychic type powers at all (and still don't), in 1985 I had a dream. The dream consisted of an encounter with a woman I hadn't seen or spoken to in 3 years and the last time was 400 miles from where I was living. I am a vivid dreamer, but this dream was more than usual, so much so that I told my wife about it when we woke up that morning (she worked with this woman). I told her about seeing this woman driving a red sports car (Porsche) and she drove very close to me, then honked and waved. About 5 hours later, while I was digging up a survey monument in the center of the road, with my boss spotting for me, I heard a beep on a horn and looked up. Within 20 feet of me was a red Porche with that lady driving it. She waved to me as she drove by. I know it was her. No mistake. I immediately dropped my digging tools and ran to the nearest pay phone (this was before cell phones) to call my wife. I have never had another experience like this before or since and have never been able to explain it. But what I will say is that NOBODY can tell me that it didn't happen. It did. That has to be what many of these witnesses feel. They saw something clearly. Something that couldn't have been a bear, a man in a suit, or any other known animal. They didn't ask to see it and weren't looking for it, but they know what they saw and no amount of ridicule or rationalization will change that. I know that feeling. They can't all be wrong.

To me, that is the most powerful evidence to date....until we have a body.

[Guest ajciani]

Obviously, by whatever metric you choose, as long as the possibility that bigfoot exists is assigned a value greater than zero, the probability that all reports are false diminishes with each added report.

So the real problem is that many skeptics emphatically refuse to assign a value greater than zero to the possibility that bigfoot exists....

For the more open-minded, though, even if you say that 99 out of 100 reports are false, and you have 1000 reports, the chance that every single one of them is false is 0.000043, or 0.0043%

This is fundamentally correct to describe a random event, but the probability needs to be measured, and so the characterization of the skeptic is a bit wrong. To ascribe a value of greater than ZERO to the probability that a sighting was "true", would require that sightings have been evaluated, and at least one sighting was determined to have been "true". So from the skeptic's point of view, the probability that BF sightings are "true" has been measured as ZERO, so the probability they are all "false" is 100%.

The example of the dice is wrong. The skeptic does not expect you to role a 6 with a dice labeled from 0 to 5. That would be a rigged game. Moreover, it would be wrong to use a multi-sided dice to describe a binary event. That is the problem. The skeptic expects that a sighting is either "true" or "false". The better example would be flipping a coin. You say that the coin has tales and heads, but after 10,000 flips, only tails has shown up. The skeptic has concluded that you are not flipping a coin, but a Mobius strip or a sphere, both of which have only 1 side. Perhaps the skeptics come from fields where things are either "true" or "false", "known" or "unknown", but Saskeptic's example shows that even biology has its partial knowns. It was either an eagle or a vulture, so it is 50% eagle and 50% vulture. Any opportunity to make a more definitive determination has long since become bot flies and worm food.

In reality, a bigfoot sighting is a multi-dimensional event. It has many individual aspects which could be "true", "false", or somewhere in between. In physics and chemistry, we make a lot of measurements which could be wrong to some degree, or explained by other things. For example, when the top quark was announced as "discovered", it had only been discovered to a 90% confidence level. That means that the measured data only fit 90% within the Standard Model, and there was still a 10% chance that future experiments could reveal that the top quark did not exist, and the Standard Model was wrong.

So in truth, an individual bigfoot sighting is not "true" or "false", but has a confidence level. It has a probability that individual aspects are explained by the existence of bigfoot, and a probability that those aspects are explained by other things. So the probability that any one sighting was "true" is non-ZERO. There are many reports which have very high confidence that a bigfoot is the explanation, just as there are some which are almost certainly bogus. Multiplying it all together, the probability that ALL bigfoot sightings are "false" is extremely low.

[Guest parnassus]

aj and other folks,

you have a fundamental misunderstanding of mathematical probability. You are mixing together wishful thinkinng, circular reasoning, confusion with common word usage, and inappropriate use of frequentist probability. Using red font doesn't change that.

Probabiity in its mathematical sense (frequentist or evidential) has to be grounded in numbers. Show me the numbers that cause you to assign a nonzero probability to each report. You can't. do it..

you are saying nothing more than you believe that some reports are true. Mathematical probability is not just your belief. You can't multiply belief x belief and come out with mathematical probability. You just come out with belief squared, so to speak.

There are two things that we can numerically say about reports: one is that no report has ever been validated with a body or body part. zero for, let's say, 20,000. A statistician doesn't look at that and think that the next report will be a validated report.

The other thing is that some reports that have been proven, objectively, to be false. I think most of those have been omitted from databases (that is a crime against science and statistics). But I think we have to admit there are some. (Peter Byrne said it was the majority). So all we know is that some reports are false and some are undetermined. We don't know of any true positives, no reports have been proven accurate. Those are the only numbers we have regarding accuracy. So from a mathematical standpoint, it is certainly possible that they are all inaccurate.

It is only by your belief that you can assign a greater than zero probability. You're just plucking it out of the air. That's fine, but you are in error if you try to make it mathematical using frequentist probability. The only way make that in any way mathematical is to use evidential probability. And by that, the likelihood that they are all inaccurate becomes greater with every report that is shown to be false. There may be, in this setting, a way of dealing with indeterminate reports statistically, but I'm not a statistician.

I am done with this. If you don't have the background to get it, I can't give it to you.

p.

Edited February 20, 2012 by parnassus

[Guest MikeG]

I don't often agree with you Parn, but I believe you to be correct here.

Mike

[Guest Jodie]

LOLOL.....when you don't have the background to discuss the subject at all, then asking the question just to dismiss the answers is an exercise in futility. I can't make a bigfoot jump in front of your car so you can see it, Parn, sorry.

[Guest MikeG]

Sorry, let me make my last post clear. I believe that Parn's last post on the strict maths of the situation is correct, but not his stance on the whole BF question. My interpretation is that he is saying we don't have enough information on which to be making a purely mathmatical/ statistical statement about the probability of all sightings being false, and I agree with that.

That doesn't in any way imply that I agree that all sightings are false.

Mike

[Guest Jodie]

Edited February 20, 2012 by Jodie

[Guest WesT]

You claim that the absence of bigfoot roadkill affects the probability that they exist.

He may have just forgot to finish the sentence. No roadkill "that we know of". Skeptics often leave the "that we know of" part out. Not sure why. Well, I've got a good idea why, but let's avoid that one. Parn is right in that a bf/sas (if it exist) must have, at one time or another, been hit and killed. Because I can testify they indeed have. And the day they pat me on the face with a shovel is the same day I'll quit talking about it.

Personally, I don't buy into the he lies she lies everybody lies but me thing. If just one of those reports out of the thousands is true, then that means...

Edited February 20, 2012 by WesT

[Cotter]

If WesT was a statisticion, and had a close up, personal Class A encounter, could he then assign a probability greater than zero?

[Guest WesT]

Well I'm not, but the answer is yes but only on a personal level. There's nothing wrong with being skeptical, just remember the words "that we know of" and you'll cruise along just fine. If someone is clairvoyant, a heads up would be appreciated.

[Guest]

Sorry if this link has already been posted

http://www.sciencedaily.com/releases/2011/01/110125092233.htm

Sounds like first hand observations that are immediately recorded, or the first time the witness retells their story are the most reliable, making the investigators question "How many others have you told?" all the more relevant.

[Guest rig416]

What Is The Statistical Probability That All Sightings Are False? .....was the original question.

I am wondering something a little different.

What is the statistical probability that all of these "false" sightings are describing the same sort of thing? An "apeman".....

What the heck are the odds of that?

So if all the sighting are false (for arguments sake) not only are they false but they are false in the same way....?

It is the number of sightings over time (hundreds of years) that keeps me interested in this topic.

How likely is it that all these people from different times, cultures & languages all misinterpret the same general thing? Always an ape?

Why don't we get reports of the extinct American Lion or Smilodon (sabertooth cat) both lived in the US until about 10-12,000 years ago and both look a lot more like a bear in general shape and appearance than a bipedal ape!

No Smilidon or American Lion reports that I know of......but we do hear of apes.

I don't know if the sasquatch is out there but, I have a real hard time dismissing it....

Best Regards,

RIG

Edited February 20, 2012 by rig416

[Guest]

Why don't we get reports of the extinct American Lion or Smilodon (sabertooth cat) . . .

RIG, you've just given me an idea for an exercise in crypto-witness reliability: Let's say we built a website about sightings of saber-toothed cats, and we welcomed witnesses to enter narratives of their sightings. We could make our site look very welcoming, explain how such creatures used to be here not that long ago, that Native Americans knew them and interacted with them, etc. We could offer our best case for evidence that such creatures exist and describe on our site how hundreds of ordinary people have reported such animals. Despite their risk of persecution, brave people from all over have shared their stories of encounters with real, live saber-tooths!

Would we have people submitting reports to our database? (I'd say yes.)

Would their accounts read as any less reliable than the bulk of bigfoot accounts? (I'd say no.)

If we had credible accounts reported to our database, with sane, rational people reporting unambiguous sightings of saber-toothed cats, how many of those would we need before we should consider that there must actually be saber-tooths out there?