# Huerta88 - your handle hurts you **URL:** \ **Category:** The BBQ Pit\ **Created:** [May 26, 2006, 5:52pm UTC](https://boards.straightdope.com/t/huerta88-your-handle-hurts-you/358344 "2006-05-26T17:52:23Z")\ **Posts on this page:** 20\ **Page:** 25
**Author:** ![Left\_Hand\_of\_Dorkness](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/left_hand_of_dorkness/32/7156_2.png) [@Left\_Hand\_of\_Dorkness](https://boards.straightdope.com/u/Left_Hand_of_Dorkness)\ **Post date:** [June 6, 2006, 4:47pm UTC](https://boards.straightdope.com/t/huerta88-your-handle-hurts-you/358344/481 "2006-06-06T16:47:12Z")
[QUOTE=Malacandra] On any grounds other than ideological ones? _Hypothetically_, were there on average fifty false claims for every true one (which I do not in fact believe to be the case), do you really not think there would be more grounds for scepticism than if there were fifty true claims for every false one? [/QUOTE] I really don’t think so. I really, truly, honestly, and sincerely don’t think so. Because: a) If there is ever a single false claim, then there is grounds for skepticism; and b) If there is ever a single true claim, then there is grounds for bothering to examine the facts. Because I know for a fact that there are true claims, then my job is to determine whether **this claim in front of me** is a true claim. Knowing how many false claims there are does not help me make this determination. If you disagree–if you believe that knowing the number of false claims helps me determine whether this claim is false–can you explain, specifically, how it helps? Daniel ---
**Author:** ![Maeglin](https://avatars.discourse-cdn.com/v4/letter/m/8baadc/32.png) [@Maeglin](https://boards.straightdope.com/u/Maeglin)\ **Post date:** [June 6, 2006, 11:40pm UTC](https://boards.straightdope.com/t/huerta88-your-handle-hurts-you/358344/482 "2006-06-06T23:40:38Z")
[QUOTE=Malacandra] Oh, I’m all for getting the most specific and applicable stats we can, believe me. It’s just that you appear to me to be arguing that unless we have _every_ stat, and have also refuted _every possible_argument as to why each of them could be wrong, we should pay no attention to them whatever. [/QUOTE] Including every conceivable variable in a model yields diminishing returns. What is important is controlling for critical variables. Failure to do so yields **omitted variable bias** , which can render the effects you claim to observe completely worthless. A so-called statistic that is generated by a misspecified model is worse than worthless: it is misleading. ---
**Author:** ![Zoe](https://avatars.discourse-cdn.com/v4/letter/z/a4c791/32.png) [@Zoe](https://boards.straightdope.com/u/Zoe)\ **Post date:** [June 7, 2006, 6:11am UTC](https://boards.straightdope.com/t/huerta88-your-handle-hurts-you/358344/483 "2006-06-07T06:11:31Z")
> [@](#): > > **Ellis Dee** : Sorry, I thought I was in the Lying Whore thread. astro created the GD thread to try and end the hijack to that thread. Didn’t seem to take. Perhaps people just really wanted to scream at Huerta for another 20 pages, and it’s no fun to try and do that in GD? I did appreciate your efforts to redirect the statistics arguments in that direction. You did try. But it wasn’t _our_ screaming at Huerta88\* that surrounded your post. My first post in the entire LW thread was on [page 17, post#838.](http://boards.straightdope.com/sdmb/showthread.php?t=366822&page=17&pp=50): > [@](#): > > **you with the face** , I see many things as you do. This thread has been unpleasant. But that’s not quite the word. Not very strident, now, really. That was followed by a bantam rooster who made assumptions about my position on the situation at Duke and who used diminishing and patronizing terms without any reason except provocation. I had not attacked _him_ or his position specifically: > [@](#): > > **Huerta88** : It’s awful, dearie. But maybe not quite as awful as for the three men who have spent time in jail, and still yet face criminal charges, based on the incomprehensible allegations (and by incomprehensible, I mean a woman who allleges that twenty men, no, no men, no three men, one with a moustache, or rather, no moustache, raped her) of a woman who had sex with three other men on the day of the “assault.” Sorry this thread has upset you, hun bun. > > I’d imagine this fact-pattern has upset the families of the lax players involved, at least a little bit. This post by **Huerta88** was followed by another by **Huerta** , one by Lochdale, another by Huerta88, another by Ellis Dee, another by Huerta88, and one by DragonAsh before **Monstro** finally posted. And the beautiful irony is that in the middle of this barrage of ranting and screaming, **Ellis Dee** , you posted this: > [@](#): > > So much so that the statistics issue is completely moot at this point. And to those still desiring to argue the relevance of the statistics, there is an actual thread devoted to it in GD. Why not argue it there? Or is the desire to rant and scream in this thread too overpowering? I agree with **Ellis Dee** except about who had been doing most of the screaming. It practically became his blog for a while. I’m glad you agree that the statistics are meaningless to the Duke case. ---
**Author:** ![EllisDee](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/ellisdee/32/4531_2.png) [@EllisDee](https://boards.straightdope.com/u/EllisDee)\ **Post date:** [June 7, 2006, 8:22am UTC](https://boards.straightdope.com/t/huerta88-your-handle-hurts-you/358344/484 "2006-06-07T08:22:03Z")
[QUOTE=Zoe] I did appreciate your efforts to redirect the statistics arguments in that direction. You did try. But it wasn’t _our_ screaming at Huerta88\* that surrounded your post. [/quote] Perhaps it was the dozen pages prior to it? > [@](#): > > I agree with **Ellis Dee** except about who had been doing most of the screaming. It practically became his blog for a while. Your definition of “most” seems to be “since I joined the thread.” If you extend that same definition to me, my point stands. ---
**Author:** ![Malacandra](https://avatars.discourse-cdn.com/v4/letter/m/45deac/32.png) [@Malacandra](https://boards.straightdope.com/u/Malacandra)\ **Post date:** [June 7, 2006, 10:23am UTC](https://boards.straightdope.com/t/huerta88-your-handle-hurts-you/358344/485 "2006-06-07T10:23:11Z")
[QUOTE=you with the face] And the reason why I say this is because even if the witness was able to tell maroons from reds 100% of the time during the “reliability test”, but maintained a 95% proficiency with respect to reds from maroons, the probability that they’d be able to correctly identify the right car from a whole pop of reds and maroons (with 2% maroon prevalence) would still be only **29%**. Which is shockingly close to the same number you achieve when sensitivity is 95% (28%). [/quote] No shock about it. The mathematical formula you used looked a bit round-the-houses to me compared to the simple method of multiplying .95 by 980, .95 by 20, etc, etc, but it’s not exactly scary that the two methods should come up with the same answer. > [@you with the face](#): > > So despite the fact that the witness was able to correctly spot the “needle in the haystack” 100% \<\\> of the time under test conditions (and made a few slipups with the reds), according to you they are unreliable. With that kind of logic, no one would take a screening test out of fear that they’d get a false positive. But amazingly, screening tests are used on a routine basis and do a lot of good. Ask yourself why. Oh, I already know why people take screening tests. It’s because the value of a true positive far outweighs the negative value of a false positive. If I falsely test positive for prostate cancer, I’m in for a few anxious moments. But if I truly test positive for prostate cancer, I can get timely medical intervention that may add years to my life. I don’t mind an unreliable test in that case, as long as it’s biassed against false _negatives_. The case is altered however when we’re talking about a testimony in a court of law. We’re not presuming that a false positive is any more acceptable than a false negative - at least, I sure hope we’re not. And in that case it is very much to the point that a 95% reliability achieved under unrealistic conditions maps to barely more than 28% reliability in the actual population. > [@you with the face](#): > > Are all cars in the city, state, or country equally likely to be at the scene of the crime exactly when it took place? For the purposes of the mathematical problem we were assuming so, and this was pretty much stated. > [@you with the face](#): > > Cause that’s what “random” means. If I have a bag full of marbles and pull one of it, I’m assuming that each marble has an equal chance of being grabbed. > > The sides of a coin have an equal chance of landing when I flip it. And you believe you are educating me in what way…? > [@you with the face](#): > > If a crime has taken place and no one knows for sure who did it, there’s only going to be a select few who are potential suspects. The police isn’t going to think someone who was in the south side of town is a potential suspect in a hit-and-run investigation that took place in the north side. Not all maroon cars that are registered are equally likely to have been involved in a specific hit-and-run incident. If the driver was said to have been male, the list of suspects do not include all the men in the town. All true so far as it goes, and all irrelevant to the meat of the matter: that given a mathematical problem that specifies that there is a particular pool of cars that are deemed equally likely to be suspects, and a witness who has tested on a balanced sample of red and maroon cars to be 95% able to identify red as red and maroon as maroon, the witness’s probability of correctly identifying a maroon car from a highly skewed population falls to about 28-29%. > [@you with the face](#): > > But hey, don’t take my word for it. See “random.” Then tell me if you still don’t see the difference. Thank you, I already know what “random” means. > [@you with the face](#): > > > [@Malacandra](#): > > > > Certainly we should consider to an extent the plausibility that an out-of-town, or even out-of-state, car needs to be included in the population. But we were taking a comparatively simple mathematical exercise, in which the lockedness of the room was taken as a given. > > That given shouldn’t be taken at face value when you are trying to prove someone is illogical. This discussion is about more than mathematics. Too right. It’s proving to be about your attachment to the 95% reliability of the key witness as being applicable regardless of what the sums say. > [@you with the face](#): > > > [@Malacandra](#): > > > > Something is begging to be laughed at, but it’s not the logic. > > I just had to explain what “random” means to you because apparently you don’t know. Yet you swear up and down that you are right and I’m wrong. I think that’s pretty funny. No, you chose loftily to inform me what “random” means, but I do already know perfectly well, thanks. > [@you with the face](#): > > > [@Malacandra](#): > > > > Can’t recall Zoe’s random number generator so I’ll have to just run with the counter-arguments you’re providing for yourself. > > Here’s the thing about Zoe’s random number generator which illustrates the error you are making: > > [Quote=Zoe] > The generator will spit out a string of numbers and it would be easy to say incredlously “What are the odds that the generator would pick these particular integers, as opposed to the many other numbers it could have?” > > And when you sit down and do the math, it would seem amazing. The probability of picking a 7, 14, 9, 38, 24, … AND a 33 is extremely small. What are the odds of this happening? It’s unbelievable! Except that its not, because you know that the generator will pick some numbers and it just happened to be those. In effect, you are looking at a past event and determining that it is unlikely just because maroon colored cars are “rare”. But any event is rare if you seize upon superficial characteristics. Such as car color. [/quote] Forgive my obtuseness, but I don’t see how these two are analogous at all. If it were established that the car really _was_ maroon, and we were arguing about the unlikeliness of it being so, then you’d have a case. But in the context of this very simple mathematical problem, the colour of the car is the very question that hangs in the balance. A better analogy would be if you told me that you had seen today’s winning lottery numbers only yesterday as a telephone number on a billboard. I might grant you an excellent memory for 12-digit numbers, but I’d still consider it more likely that you’d misremembered a digit than not. Whereas if we saw a story in the paper about an unfortunate gambler who would have won that week if only he had used his own telephone number… well, that’s a non-story: there are millions of telephone subscribers in the country, and the paper can report on any of them that happens to write in and report the so-called “coincidence”. > [@you with the face](#): > > In effect, you are looking at a past event and determining that it is unlikely just because maroon colored cars are “rare”. But any event is rare if you seize upon superficial characteristics. Such as car color. But in this instance, that superficial characteristic was the sole key fact that the eyewitness was able to bring. > [@Maeglin](#): > > Including every conceivable variable in a model yields diminishing returns. What is important is controlling for critical variables. Failure to do so yields omitted variable bias, which can render the effects you claim to observe completely worthless. A so-called statistic that is generated by a misspecified model is worse than worthless: it is misleading. Quite. Just as a so-called witness reliability that was established by an unrealistic test is worthless and misleading. > [@Left Hand of Dorkness](#): > > I really don’t think so. I really, truly, honestly, and sincerely don’t think so. Because: > a) If there is ever a single false claim, then there is grounds for skepticism; and > b) If there is ever a single true claim, then there is grounds for bothering to examine the facts. > > Because I know for a fact that there are true claims, then my job is to determine whether this claim in front of me is a true claim. Knowing how many false claims there are does not help me make this determination. > > If you disagree–if you believe that knowing the number of false claims helps me determine whether this claim is false–can you explain, specifically, how it helps? > > Daniel I suppose it helps when you are determining where to allocate finite resources. Given infinite manpower and money I’d investigate all claims as exhaustively as humanly possible. Without that, I’d prefer to concentrate on the claims that had a history of being true fifty times for every time they were false, rather than the claims for which the reverse was true. It’s a case of furthering the ends of justice to the greatest extent possible within the constraints. I don’t say I’d want to ignore the unlikely claims entirely, but I’d be inclined to a little world-weary cynicism and perhaps a touch of perfunctoriness. Of course, political concerns might oblige me to treat all claims the same, but on the whole, more crimes would go unpunished as a result. ---
**Author:** ![you\_with\_the\_face](https://avatars.discourse-cdn.com/v4/letter/y/ecccb3/32.png) [@you\_with\_the\_face](https://boards.straightdope.com/u/you_with_the_face)\ **Post date:** [June 7, 2006, 1:32pm UTC](https://boards.straightdope.com/t/huerta88-your-handle-hurts-you/358344/486 "2006-06-07T13:32:24Z")
[QUOTE=Malacandra] Oh, I already know why people take screening tests. It’s because the value of a true positive far outweighs the negative value of a false positive. If I falsely test positive for prostate cancer, I’m in for a few anxious moments. But if I truly test positive for prostate cancer, I can get timely medical intervention that may add years to my life. [/quote] Yeah, but also keep in mind that prostate screening tests are not given to the whole population, but rather to at risk groups. If a prostate screening test has the same parameters as your maroon-identifying witness, it would have a horrible PPV if every male in the population took the test. But when you only target men in the at-risk age group, the PPV signficantly increases. Which is why it has value. > [@](#): > > The case is altered however when we’re talking about a testimony in a court of law. We’re not presuming that a false positive is any more acceptable than a false negative - at least, I sure hope we’re not. And in that case it is very much to the point that a 95% reliability achieved under unrealistic conditions maps to barely more than 28% reliability in the actual population. So I just talked about prostate screening tests and why they have value. You should know by now such screening is not recommended to everyone in the population, and that’s specifically because that would increase the false positive rate. Apply the same reasoning to this car hypothetical. A hit-and-run accident will produce a handful of suspects: basically all the cars that were observed to be in the immediate vicinity when the crime took place. This is, in effect, our “at-risk” group. It’s not the entire population of the city, state, country, world, or universe. It’s clear that the lines you have drawn for your population are completely arbitrary. You might as well be including people in Siberia as part of your “population”. This is the part that you keep tripping up on, **Malacandra**. I really don’t know how to explain this any better, so perhaps we should agree to disagree. I feel like I’m talking to a wall. > [@](#): > > For the purposes of the mathematical problem we were assuming so, and this was pretty much stated. You keep emphasizing the “mathematicalness” of this problem and I’m like, so what? This discussion is not about making some numbers add up to the right thing. It’s about knowing how to apply statistics properly. Two different concepts. > [@](#): > > All true so far as it goes, and all irrelevant to the meat of the matter: that given a mathematical problem that specifies that there is a particular pool of cars that are deemed equally likely to be suspects, and a witness who has tested on a balanced sample of red and maroon cars to be 95% able to identify red as red and maroon as maroon, the witness’s probability of correctly identifying a maroon car from a highly skewed population falls to about 28-29%. It’s clear that you are only parroting back what the “New Scientist” has told you because you keep repeating the same thing over and over again. We have no reason to believe that the “particular pool of cars that are deemed equally likely to be suspects” matches anywhere close to the composition of the whole population. > [@](#): > > Thank you, I already know what “random” means. Then why did you ask a question that clearly demonstrated that you do not? > [@](#): > > Forgive my obtuseness, but I don’t see how these two are analogous at all. If it were established that the car really _was_ maroon, and we were arguing about the unlikeliness of it being so, then you’d have a case. But in the context of this very simple mathematical problem, the colour of the car is the very question that hangs in the balance. The witness says they saw a maroon car. You doubt that witness. Your reasoning boils down to the hypothetical fact that maroon cars are rare. This is no different than doubting me when I say that a man named Bucky Bugeyed stole 10 bucks from me. How many men out there are named Bucky Bugeyed? Only one out of a global population of 6.6 billion? According to The Logic of **Malacandra** , this means this was an improbable event and therefore unlikely. So perhaps I just heard his name wrong, eh? Maybe it’s really Bucky Beaver. There’s a lot more guys with that name and they _do_ sound a lot alike. So Bucky Beaver it is! You are committing this error, whether you are aware of it or not. Frankly, I don’t see why you can’t see that by now. > [@](#): > > A better analogy would be if you told me that you had seen today’s winning lottery numbers only yesterday as a telephone number on a billboard. No, this is a crappy analogy. > [@](#): > > Quite. Just as a so-called witness reliability that was established by an unrealistic test is worthless and misleading. Reliability is completely separate from positive predictive value (or probability). “[Reliability](http://www.biology-online.org/dictionary/Test-retest_reliability)” is a term that has a precise meaning in the scientific community and you betray ignorance when you use it inappropriately. It doesn’t look like I’m getting through to you, so I quit. Hopefully all this explaining wasn’t done in vain and I gave you at least a little something to chew on. ---
**Author:** ![Malacandra](https://avatars.discourse-cdn.com/v4/letter/m/45deac/32.png) [@Malacandra](https://boards.straightdope.com/u/Malacandra)\ **Post date:** [June 7, 2006, 2:42pm UTC](https://boards.straightdope.com/t/huerta88-your-handle-hurts-you/358344/487 "2006-06-07T14:42:43Z")
[QUOTE=you with the face] Yeah, but also keep in mind that prostate screening tests are not given to the whole population, but rather to at risk groups. If a prostate screening test has the same parameters as your maroon-identifying witness, it would have a horrible PPV if every male in the population took the test. But when you only target men in the at-risk age group, the PPV signficantly increases. Which is why it has value. [/quote] There’s some relevance here, I just know it. _takes out magnifying glass_ > [@you with the face](#): > > So I just talked about prostate screening tests and why they have value. You should know by now such screening is not recommended to everyone in the population, and that’s specifically because that would increase the false positive rate. > > Apply the same reasoning to this car hypothetical. A hit-and-run accident will produce a handful of suspects: basically all the cars that were observed to be in the immediate vicinity when the crime took place. This is, in effect, our “at-risk” group. It’s not the entire population of the city, state, country, world, or universe. It’s clear that the lines you have drawn for your population are completely arbitrary. You might as well be including people in Siberia as part of your “population”. Okay, and your grounds for supposing that the maroon-to-red proportion in the “at-risk” group will differ from the general proportion of maroon to red within a few-mile radius would be…? Oh, because the witness said it was maroon. Beg the question much? > [@you with the face](#): > > This is the part that you keep tripping up on, **Malacandra**. I really don’t know how to explain this any better, so perhaps we should agree to disagree. I feel like I’m talking to a wall. I believe I am acquainted with the sensation. Reminds me of a line out of “Things My Girlfriend And I Have Argued About” about watching a shoal of Argument Fish being pursued by a Truth Shark, as every time we get around to the hypothetical witness’s hypothetical credibility you find some other reason to argue that the numbers we should consider are something other than the numbers in the question, mostly (as far as I can tell) because you feel that a witness who has tested 95% reliable in one set of circumstances must always remain so. > [@you with the face](#): > > You keep emphasizing the “mathematicalness” of this problem and I’m like, so what? This discussion is not about making some numbers add up to the right thing. It’s about knowing how to apply statistics properly. Two different concepts. Indeed. One’s about making the explanation fit the data, and the other’s about making the data fit the explanation. “I’m, like, so what?” is not an appropriate attitude for a professional scientist to take over mathematics! > [@you with the face](#): > > It’s clear that you are only parroting back what the “New Scientist” has told you because you keep repeating the same thing over and over again. We have no reason to believe that the “particular pool of cars that are deemed equally likely to be suspects” matches anywhere close to the composition of the whole population. We have no reason so suppose that it doesn’t, either. Indeed, it’s not impossible that in fact none of the town’s 20 maroon cars ever drive by the location in question. But in the absence of other data - and the problem didn’t provide any other - you don’t have any grounds for supposing that the local distribution is any different from the town-wide one. Oh, except that the witness said it was maroon. :rolleyes: > [@you with the face](#): > > Then why did you ask a question that clearly demonstrated that you do not? As I do know very well what “random” means, I cannot very well have knowingly asked a question that demonstrates that I do not, so you can’t expect me to meaningfully answer such a question. > [@you with the face](#): > > The witness says they saw a maroon car. > > You doubt that witness. > > Your reasoning boils down to the hypothetical fact that maroon cars are rare. Good, so you’re with me so far. In the example, there’s nothing “hypothetical” about the rarity of maroon cars. They’re outnumbered 49-1 by red, and the two colours are occasionally mistaken for each other even by people with good colour vision. Right, now we’re getting somewhere… > [@you with the face](#): > > This is no different than doubting me when I say that a man named Bucky Bugeyed stole 10 bucks from me. > > How many men out there are named Bucky Bugeyed? Only one out of a global population of 6.6 billion? According to The Logic of **Malacandra** , this means this was an improbable event and therefore unlikely. So perhaps I just heard his name wrong, eh? Maybe it’s really Bucky Beaver. There’s a lot more guys with that name and they _do_ sound a lot alike. So Bucky Beaver it is! [will to live=evaporating]Depends. How’d you learn his name? Yelled out by a passer-by who is now untraceable? Tests show that you occasionally identify a yell of “Bucky Bugeyed” as “Bucky Beaver” and vice versa? Bucky Beaver is a far more common name than Bucky Bugeyes? What are your grounds for having your supposed identification of Bucky Bugeyes taken seriously?[/wtl] Yes, if it’s an _established fact_ that a man named Bucky Bugeyed stole $10 from you then it is cretinous to burble “Wow! What are the odds of that?”. But if the question we are trying to determine is what the man’s name was… > [@you with the face](#): > > You are committing this error, whether you are aware of it or not. Frankly, I don’t see why you can’t see that by now. Oy. :smack: Am I right in thinking that you would sink if dropped into a bath of mercury? Suppose I say that David Beckham (England football captain) beat me up and stole my wallet. He is a well-known national figure and his face is regularly in the papers, and it is extremely likely that I would recognise him if I saw him. For all that, it is possible that someone who merely _looks_ like him is the culprit. My recognition of his face is the sole relevant criterion for this particular question. Now, _setting aside_ all question of what the hell multimillionaire Beckham would want with my wallet, and _in the absence_ of other information concerning Beckham’s movements, what is the likelihood that I was robbed by one particular man in the whole country, rather than one of possibly thousands who happen to look a lot like him? Can you not see that if my picture appears in the paper along with Beckham’s after he has been convicted by due process of law of robbery with violence against me, it is _then_ that only an idiot would say “Wow! What were the odds of that?”? > [@you with the face](#): > > No, this is a crappy analogy. Your well-thought-out refutation has completely drawn the wind from my sails. Oh, wait, no it hasn’t. > [@you with the face](#): > > Reliability is completely separate from positive predictive value (or probability). “[Reliability](http://www.biology-online.org/dictionary/Test-retest_reliability)” is a term that has a precise meaning in the scientific community and you betray ignorance when you use it inappropriately. This is you not beating anyone over the head with your doctorate, then? :dubious: As you well know, I was not aiming for precise usage of a scientific term in addressing **Maeglin** but simply using the word in its colloquial sense. When struggling with the grade-school math and logic, resort to professional condescension, huh? > [@you with the face](#): > > It doesn’t look like I’m getting through to you, so I quit. Hopefully all this explaining wasn’t done in vain and I gave you at least a little something to chew on. Whereupon the good Doctor checks out of the argument, declaring herself the winner. ---
**Author:** ![you\_with\_the\_face](https://avatars.discourse-cdn.com/v4/letter/y/ecccb3/32.png) [@you\_with\_the\_face](https://boards.straightdope.com/u/you_with_the_face)\ **Post date:** [June 7, 2006, 4:06pm UTC](https://boards.straightdope.com/t/huerta88-your-handle-hurts-you/358344/488 "2006-06-07T16:06:10Z")
> [@Malacandra](#): > > Okay, and your grounds for supposing that the maroon-to-red proportion in the “at-risk” group will differ from the general proportion of maroon to red within a few-mile radius would be…? Oh, because the witness said it was maroon. Beg the question much? Read my hypothetical and see if any of this gets through: There’s a hit-and-run accident on the corner of South and Main St. With me so far? A few seconds before the incident, a surveillance camera upstream from the accident catches four cars driving down the street. The front-most car is the victim’s car (who ended up dying from the collision). The three subsequent cars are considered suspects because of the timing of their passing in relation to the incident. Two of these suspect cars are red. One of them is maroon. This has been verified by cross-referencing the license plates with registration data. The prevalence of maroons in this “population” of suspects is 33%.\* An eye-witness to the crime saw the accident and claims that the culpable car was maroon. Prosecution investigates, finds some other evidence (such as the surveillance video), and the driver of the maroon is arrested and taken to court. The prosecution says the witness has been shown to accurately spot maroon cars with 95% proficiency. The witness goes on to testify that he saw a maroon car commit the crime. You are a lawyer for the defense. You claim the witness is unreliable because internationally, maroon cars only make up 2% of the car population. Ergo, the witness can not be beleived and the defendant is innocent. The jury bursts out in laughter. The judge bangs his gavel for order, but stops when she too is overcome with the giggles. She adjourns court for a recess after the baliff starts convulsing. You see, he has epilepsy and its triggered when he laughs too hard. The defendant, on the other hand, starts crying like a baby. Because he realizes that he wasted his money on a charlatan of a lawyer and knows he has no chance in hell of getting off now. You are confused by all these reactions, because according to the _New Scientist_, your argument was rock solid and beyond dispute. So you stand in the middle of the court room, scratching your head, breathing out of your mouth. A cowlick pops up on the back of your head. The lawyer for the prosecution leans back in her seat and smiles, amused with the circus around her. She’s so glad that she had had the idea of slipping a copy of _New Scientist_ in your mailbox a week before the trial. Very glad. Roll credits. \*The witness now has an 85% of being correct. The “at-risk” population is the population you need to be concerned about. Not the entire population of cars in the whole world. Or even the country. Or even the state. Or even the city. Not even _gasp_ the county! ---
**Author:** ![you\_with\_the\_face](https://avatars.discourse-cdn.com/v4/letter/y/ecccb3/32.png) [@you\_with\_the\_face](https://boards.straightdope.com/u/you_with_the_face)\ **Post date:** [June 7, 2006, 4:23pm UTC](https://boards.straightdope.com/t/huerta88-your-handle-hurts-you/358344/489 "2006-06-07T16:23:11Z")
[QUOTE=Malacandra] This is you not beating anyone over the head with your doctorate, then? :dubious: As you well know, I was not aiming for precise usage of a scientific term in addressing **Maeglin** but simply using the word in its colloquial sense. When struggling with the grade-school math and logic, resort to professional condescension, huh? [/QUOTE] It’s not condescending to advise you to use words properly, as they are defined and understood in the field of applied statistics (you know, the subject matter that we are discussing?). And if this innocuous information counts as “beating anyone over the head with your doctorate”, you need to stop being so insecure. Everytime you use “reliable” as you are using it you are essentially saying to the world “I don’t know what the hell I’m talking about! Please laugh and point at me!” Which the whole world has been doing. ---
**Author:** ![you\_with\_the\_face](https://avatars.discourse-cdn.com/v4/letter/y/ecccb3/32.png) [@you\_with\_the\_face](https://boards.straightdope.com/u/you_with_the_face)\ **Post date:** [June 7, 2006, 4:45pm UTC](https://boards.straightdope.com/t/huerta88-your-handle-hurts-you/358344/490 "2006-06-07T16:45:16Z")
> [@Malacandra](#): > > Suppose I say that David Beckham (England football captain) beat me up and stole my wallet. He is a well-known national figure and his face is regularly in the papers, and it is extremely likely that I would recognise him if I saw him. For all that, it is possible that someone who merely looks like him is the culprit. Okay, I’m with you so far. Nothing egregious. > [@](#): > > My recognition of his face is the sole relevant criterion for this particular question. Now, setting aside all question of what the hell multimillionaire Beckham would want with my wallet, and in the absence of other information concerning Beckham’s movements, what is the likelihood that I was robbed by one particular man in the whole country, \*\* rather than one of possibly thousands who happen to look a lot like him?\*\* Assuming that all guys who look like Beckham (including Beckham) have equal chance of being the culprit, the likelihood that you were robbed by Beckham is no different had you been robbed by his evil twin brother, the sexy janitor at the McDonald’s down the street, or Charlie the hot bus driver. In the absence of evidence, means that _no one_ has been identified as a suspect. Why should Beckham get any special considerations that Charlie the bus driver doesn’t? Charlie hasn’t ever stolen anything in his life. Charlie is a good, God-fearing man. ---
**Author:** ![Left\_Hand\_of\_Dorkness](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/left_hand_of_dorkness/32/7156_2.png) [@Left\_Hand\_of\_Dorkness](https://boards.straightdope.com/u/Left_Hand_of_Dorkness)\ **Post date:** [June 7, 2006, 6:02pm UTC](https://boards.straightdope.com/t/huerta88-your-handle-hurts-you/358344/491 "2006-06-07T18:02:45Z")
[QUOTE=Malacandra] I suppose it helps when you are determining where to allocate finite resources. Given infinite manpower and money I’d investigate all claims as exhaustively as humanly possible. Without that, I’d prefer to concentrate on the claims that had a history of being true fifty times for every time they were false, rather than the claims for which the reverse was true. It’s a case of furthering the ends of justice to the greatest extent possible within the constraints. I don’t say I’d want to ignore the unlikely claims entirely, but I’d be inclined to a little world-weary cynicism and perhaps a touch of perfunctoriness. Of course, political concerns might oblige me to treat all claims the same, but on the whole, more crimes would go unpunished as a result. [/QUOTE] I’m not sure “finite resources” is the trigger for weighing likelihood; instead, I think that “inadequate resources” should be the trigger. If there are ten reports of rape and I only have the rsources to examine three of them fully, or nine of them perfunctorily, then it makes sense for me to engage in some sort of triage, deciding which cases are likeliest to be prosecutable, which rapists are likeliest to be repeat offenders, etc. Part of that awful calculus may involve deciding which allegations are likeliest to be true. However, I’ve seen no evidence that this is the case in Durhum, that the DA’s office lacks the resources to investigate all rape allegations adequately. If we stipulate that they have the resources to perform an adequate initial investigation of every rape allegation, then do you agree that the argument about statistical likelihoods (assuming that the statement “some, but not all, rape allegations with a certain trait are legitimate accusations” is a true statement) is irrelevant? Daniel ---
**Author:** ![you\_with\_the\_face](https://avatars.discourse-cdn.com/v4/letter/y/ecccb3/32.png) [@you\_with\_the\_face](https://boards.straightdope.com/u/you_with_the_face)\ **Post date:** [June 7, 2006, 6:38pm UTC](https://boards.straightdope.com/t/huerta88-your-handle-hurts-you/358344/492 "2006-06-07T18:38:42Z")
And also **Malacandra** , note the interesting similarity between these two posts: > [@Malacandra](#): > > My recognition of his face is the sole relevant criterion for this particular question. Now, setting aside all question of what the hell multimillionaire Beckham would want with my wallet, and in the absence of other information concerning Beckham’s movements, **what is the likelihood that I was robbed by one particular man in the whole country, rather than one of possibly thousands who happen to look a lot like him?** > [@YWTF's description of Zoe's random generator](#): > > The generator will spit out a string of numbers and it would be easy to say incredlously **“What are the odds that the generator would pick these particular integers, as opposed to the many other numbers it could have?”** > > And when you sit down and do the math, it would seem amazing. The probability of picking a 7, 14, 9, 38, 24, … AND a 33 is extremely small. What are the odds of this happening? It’s unbelievable! Except that its not, because you know that the generator will pick some numbers and it just happened to be those. (bolding mine) ---
**Author:** ![VegemiteMoose](https://avatars.discourse-cdn.com/v4/letter/v/df788c/32.png) [@VegemiteMoose](https://boards.straightdope.com/u/VegemiteMoose)\ **Post date:** [June 7, 2006, 6:54pm UTC](https://boards.straightdope.com/t/huerta88-your-handle-hurts-you/358344/493 "2006-06-07T18:54:41Z")
Holy fucking hell **you with the face** , how do you not get this?. How many times can people try to get it through to you that talking about **claims** of facts are not the same thing as talking about **actual, verifiable** facts?!? That is why the random number generator analogy fails. Because in that analogy you are assuming that _you know the answer_. Try this instead: I happen to have a random number generator sitting here (picks 6 numbers between 1 and 49 - just like the lotto). Let er rip. Okay, it picked 3,17, 22, 24, 47 and 49. Or so I _claim_. Knowing nothing about me, and not being able to verify this draw of numbers, how do you evaluate the **chance** that my **claim** is true? WITHOUT INTRODUCING ANY NEW EVIDENCE. No digital cameras or witnesses or anything. Get it? ---
**Author:** ![you\_with\_the\_face](https://avatars.discourse-cdn.com/v4/letter/y/ecccb3/32.png) [@you\_with\_the\_face](https://boards.straightdope.com/u/you_with_the_face)\ **Post date:** [June 7, 2006, 7:27pm UTC](https://boards.straightdope.com/t/huerta88-your-handle-hurts-you/358344/494 "2006-06-07T19:27:54Z")
[QUOTE=VegemiteMoose] That is why the random number generator analogy fails. Because in that analogy you are assuming that _you know the answer_. [/quote] You don’t understand the analogy, then. It’s flown so far over your head that you must have never seen it. So let me walk you through it: I tell you a random number generator has spit out 5 integers from 1 to 100. Let’s say they are 56, 12, 4, 35, and 99. You do the math and the odds of these 5 numbers coming up out of all the combinations of numbers between 1 and 100 is extremely low. Nevermind the fact that any combination of 5 numbers between 1 and 100 will have these same odds. You are so fixated on the odds that you swear and up down that this is unlikely. So you say you don’t believe me because of this. And I laugh at you. Now please explain how this is differs from the Beckham analogy put forth by **Malacandra**. Since you’ve declared that I “don’t get it” surely you can explain where my logic has gone off track. ---
**Author:** ![VegemiteMoose](https://avatars.discourse-cdn.com/v4/letter/v/df788c/32.png) [@VegemiteMoose](https://boards.straightdope.com/u/VegemiteMoose)\ **Post date:** [June 7, 2006, 8:27pm UTC](https://boards.straightdope.com/t/huerta88-your-handle-hurts-you/358344/495 "2006-06-07T20:27:23Z")
Of course I don’t believe you. **Because** the odds are so against it. Kind of like the lottery. They actually force you to **verify** your claim. And if you can’t, they laugh at you. All you’ve done is change the hypothetical to place **yourself** in the position of “knowing the answer” again. Answer the question at the end of my previous post please. With **my** claim of generated numbers. And you being the one unable to verify the truth. ---
**Author:** ![Left\_Hand\_of\_Dorkness](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/left_hand_of_dorkness/32/7156_2.png) [@Left\_Hand\_of\_Dorkness](https://boards.straightdope.com/u/Left_Hand_of_Dorkness)\ **Post date:** [June 7, 2006, 8:40pm UTC](https://boards.straightdope.com/t/huerta88-your-handle-hurts-you/358344/496 "2006-06-07T20:40:10Z")
[QUOTE=VegemiteMoose] I happen to have a random number generator sitting here (picks 6 numbers between 1 and 49 - just like the lotto). Let er rip. Okay, it picked 3,17, 22, 24, 47 and 49. Or so I _claim_. Knowing nothing about me, and not being able to verify this draw of numbers, how do you evaluate the **chance** that my **claim** is true? WITHOUT INTRODUCING ANY NEW EVIDENCE. No digital cameras or witnesses or anything. Get it? [/QUOTE] How do I evaluate **the chance** that your claim is true? I look at the benefits to you of lying to me, how likely it is that you know that I can’t verify your draw, and the potential problems caused by my incorrectly evaluating the chance that the claim is true. If it turns out that there’s a huge problem caused by my incorrectly evaluating the chance, and there’s no probelm caused by my refusing to evaluate the chance barring further information, then I refuse to evaluate the chance. Yes, I know it’s not the answer you’re looking for–but if you further modify the analogy, you remove it from the realm of relevancy. Daniel ---
**Author:** ![you\_with\_the\_face](https://avatars.discourse-cdn.com/v4/letter/y/ecccb3/32.png) [@you\_with\_the\_face](https://boards.straightdope.com/u/you_with_the_face)\ **Post date:** [June 7, 2006, 8:51pm UTC](https://boards.straightdope.com/t/huerta88-your-handle-hurts-you/358344/497 "2006-06-07T20:51:11Z")
[QUOTE=VegemiteMoose] Of course I don’t believe you. **Because** the odds are so against it. Kind of like the lottery. They actually force you to **verify** your claim. And if you can’t, they laugh at you. [/quote] I’m really trying to understand your position. Maybe I’m not reading you correctly. Because the odds that the RNG would have generated that particular string of numbers (out of all the other combinations it could have generated), you doubt my claim? \*\*Even though the probability that particular string of numbers being generated is no different than any other combination? \*\* Is this what you are saying? > [@](#): > > All you’ve done is change the hypothetical to place **yourself** in the position of “knowing the answer” again. I has fuckall to do with “knowing”, and all to do with “Why shouldn’t you believe me?” Should you be skeptical of a claim that I drew the number 4 out of a hat containing 100 numbers? The probability of this is low (1/100), right? But that factoid alone should not warrant skepticism. Especially since me drawing _any_ number has 1 to 100 odds. > [@](#): > > Answer the question at the end of my previous post please. With **my** claim of generated numbers. And you being the one unable to verify the truth. If someone claimed that the RNG returned a sequence of numbers that did not appear, to my eyes, randomly selected (i.e. it looks like a series generated through some form of intelligence) then yes, that would give me pause. _Because it goes against my understanding of nature._ **However, I don’t have to compute probability to reach this conclusion because the mathematical probability of getting those numbers is actually no different had the sequence been truely random.** In other words, skepticism comes from my awareness of the world (common sense) and not math. Now if your sequence doesn’t strike me as being “unrandom”, then I have no reason to doubt you. It sounds plausible because it doesn’t go against my worldview. Probability has nothing to do with it. ---
**Author:** ![Left\_Hand\_of\_Dorkness](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/left_hand_of_dorkness/32/7156_2.png) [@Left\_Hand\_of\_Dorkness](https://boards.straightdope.com/u/Left_Hand_of_Dorkness)\ **Post date:** [June 7, 2006, 9:33pm UTC](https://boards.straightdope.com/t/huerta88-your-handle-hurts-you/358344/498 "2006-06-07T21:33:47Z")
[QUOTE=you with the face] Should you be skeptical of a claim that I drew the number 4 out of a hat containing 100 numbers? The probability of this is low (1/100), right? But that factoid alone should not warrant skepticism. Especially since me drawing _any_ number has 1 to 100 odds. [/QUOTE] This does really baffle me. I imagine you pulling a number out of a hat, looking at it, saying, “I drew a 4,” and folks shouting, “Bullshit, you lying whore!” Why? If you want to be skeptical of **ywtf’s** claim, then have at it. If you want to demand additional corroborating evidence before you’re satisfied that she drew a 4, good for you! But if you believe the hat has 99 4’s and one 17 in it, and she says she drew a 4, wouldn’t you **also** want corroboration, if the number she drew had some impact on the world (let’s say, if she drew a 4, it’d send three guys to prison for a long time)? Assuming that you’ve got the resources to achieve corroboration, why would you demand more corroboration in the first case than the second? Nobody’s objecting to the calls for corroboration. Folks are objecting to saying that the call for corroboration should be affected by the rarity of the claim, **when the claim happens on an annual basis**. Daniel ---
**Author:** ![you\_with\_the\_face](https://avatars.discourse-cdn.com/v4/letter/y/ecccb3/32.png) [@you\_with\_the\_face](https://boards.straightdope.com/u/you_with_the_face)\ **Post date:** [June 7, 2006, 9:45pm UTC](https://boards.straightdope.com/t/huerta88-your-handle-hurts-you/358344/499 "2006-06-07T21:45:05Z")
[QUOTE=Left Hand of Dorkness] This does really baffle me. I imagine you pulling a number out of a hat, looking at it, saying, “I drew a 4,” and folks shouting, “Bullshit, you lying whore!” [/quote] **Veggimite** reply to my query really baffled me. If his justification for not believing a claim about a RNG is simply like “I need to see evidence before believing anything” then that’s acceptable. But he didn’t say that. He said this: > [@](#): > > Of course I don’t believe you. **Because** the odds are so against it. Its the kind of logic that makes android’s cry. ---
**Author:** ![Zoe](https://avatars.discourse-cdn.com/v4/letter/z/a4c791/32.png) [@Zoe](https://boards.straightdope.com/u/Zoe)\ **Post date:** [June 8, 2006, 1:17am UTC](https://boards.straightdope.com/t/huerta88-your-handle-hurts-you/358344/500 "2006-06-08T01:17:50Z")
The random number generator was my hypothetical. In my hypothetical, I said this: > [@](#): > > The generator will spit out a string of numbers. So that’s a given. (I believe at the time we were talking about sixteen numbers.) The odds are the same for any sequence of sixteen numbers between 0-99. Unbelievably slim. And yet we _know_ before the numbers are generated that one sequence of sixteen numbers _will beat the odds_. The series of numbers will be generated on live television at the Oscars with **VegemiteMoose** , **YWTF** , **LHoD** , **Roger Penrose** , **Cecil** , and **Tomndebb** in attendance as witnesses and participants. Each of them will contribute one number. **VegemiteMoose** will get to choose the order and place in which people will insert numbers. The other numbers will be generated by the random number generator. The sequence of sixteen will prevail in a parallel universe if something goes wrong in this one. [Previous page](https://boards.straightdope.com/t/huerta88-your-handle-hurts-you/358344.md?page=24) [Next page](https://boards.straightdope.com/t/huerta88-your-handle-hurts-you/358344.md?page=26)