explain xkcd - User contributions [en]

Talk:2243: Star Wars Spoiler Generator

2019-12-19T02:08:56Z

172.69.69.244:

I made this JavaScript implementation of the generator: https://codepen.io/qgustavor/full/gObgBxo [[Special:Contributions/172.68.24.70|172.68.24.70]] 22:33, 18 December 2019 (UTC)

who said that the rise of skywalker would be released two days before the publishing date after stating that it's going to be released on the twentieth?

Re: Malloc, there was also a Darth Malak, the antagonist of Star Wars Knights of the Old Republic and a recurring character in the Old Republic comics [[Special:Contributions/172.69.69.244|172.69.69.244]] 02:08, 19 December 2019 (UTC)47.221.57.204

Talk:1132: Frequentists vs. Bayesians

2019-12-03T14:46:39Z

172.69.69.244: Seeing if I missed anything about the humor in the final part of the punchline.

Something should be added about the prior probability of the sun going nova, as that is the primary substantive point. "The neutrino detector is evidence that the Sun has exploded. It's showing an observation which is 35 times more likely to appear if the Sun has exploded than if it hasn't (likelihood ratio of 35:1). The Bayesian just doesn't think that's strong enough evidence to overcome the prior odds, i.e., after multiplying the prior odds by 35 they still aren't very high." - http://lesswrong.com/r/discussion/lw/fe5/xkcd_frequentist_vs_bayesians/ [[Special:Contributions/209.65.52.92|209.65.52.92]] 23:51, 9 November 2012 (UTC)

Note: taking that bet would be a mistake. If the Bayesian is right, you're out $50. If he's wrong, everyone is about to die and you'll never get to spend the winnings. Of course, this meta-analysis is itself a type of Bayesian thinking, so [http://lmgtfy.com/?q=dunning-kruger+effect Dunning-Kruger Effect] would apply. - [[User:Frankie|Frankie]] ([[User talk:Frankie|talk]]) 13:50, 9 November 2012 (UTC)
: You don't think you could spend fifty bucks in eight minutes? ;-) (PS: wikipedia is probably a better link than lmgtfy: {{w|Dunning-Kruger effect}}) -- [[User:IronyChef|IronyChef]] ([[User talk:IronyChef|talk]]) 15:35, 9 November 2012 (UTC)
Randall has referenced the Labyrinth guards before: [http://xkcd.com/246/ xkcd 246:Labyrinth puzzle]. Plus he has satirized p<0.05 in [http://www.explainxkcd.com/wiki/index.php?title=882:_Significant xkcd 882:Significant]--[[User:Prooffreader|Prooffreader]] ([[User talk:Prooffreader|talk]]) 15:59, 9 November 2012 (UTC)

A bit of maths. Let event N be the sun going nova and event Y be the detector giving the answer "Yes". The detector has already given a positive answer so we want to compute P(N|Y). Applying the Bayes' theorem:
: P(N|Y) = P(Y|N) * P(N) / P(Y)
: P(Y|N) = 1
: P(N) = 0.0000....
: P(Y|N) * P(N) = 0.0000...
: P(Y) = p(Y|N)*P(N) + P(Y|-N)*P(-N)
: P(Y|-N) = 1/36
: P(-N) = 0.999999...
: P(Y) = 0 + 1/36 = 1/36
: P(N|Y) = 0 / (1/36) = 0
Quite likely it's not entirely correct. [[User:Lmpk|Lmpk]] ([[User talk:Lmpk|talk]]) 16:22, 9 November 2012 (UTC)

Here's what I get for the application of Bayes' Theorem:
: P(N|Y) = P(Y|N) * P(N) / P(Y): = P(Y|N) * P(N) / [P(Y|N) * P(N) + P(Y|~N) * P(~N)]
: = 35/36 * P(N) / [35/36 * P(N) + 1/36 * (1 - P(N))]
: = 35 * P(N) / [35 * P(N) - P(N) + 1]
: < 35 * P(N)
: = 35 * (really small number)

So, if you believe it's extremely unlikely for the sun to go nova, then you should also believe it's unlikely a Yes answer is true.

I wouldn't say the comic is about election prediction models. It's about a long-standing dispute between two different schools of statisticians, a dispute that began before Nate Silver was born. It's possible that the recent media attention for Silver and his ilk inspired this subject, but it's the kind of geeky issue Randall would typically take on in other circumstances too. [[User:MGK|MGK]] ([[User talk:MGK|talk]]) 19:44, 9 November 2012 (UTC)

I agree - this is not directed at the US-presidential election. I also want to add, that Bayesian btatistics assumes that parameters of distributions (e.g. mean of gaussian) are also random variables. These random variables have prior distributions - in this case p(sun explodes). The Bayesian statistitian in this comic has access to this prior distribution and so has other estimates for an error of the neutrino detector. The knowlege of the prior distribution is somewhat considered a "black art" by other statisticians.

My personal interpretation of the "bet you $50 it hasn't" reply is in the case of the sun going nova, no one would be alive to ask the neutrino detector, the probability of the sun going nova is always 0. [[User:Paps|Paps]]

:Yes, you would be able to ask. While neutrinos move almost at speed of light, the plasma of the explosion is significally slower, [http://en.wikipedia.org/wiki/Supernova 10% of speed of light tops]. You will have more that hour to ask. (Note that technically, sun can't go [http://en.wikipedia.org/wiki/Nova nova], because nova is white dwarf with external source of hydrogen. It can (and will), however, go supernova, which I assume is what Randall means.) -- [[User:Hkmaly|Hkmaly]] ([[User talk:Hkmaly|talk]]) 09:19, 12 November 2012 (UTC)

:: Our sun will not go supernova, as it has insufficient mass. It will slowly become hotter, rendering Earth uninhabitable in a few billion years. In about 5 billion years it will puff up into a red giant, swallowing the inner planets. After that, it will gradually blow off its lighter gasses, eventually leaving behind the core, a white dwarf. [[Special:Contributions/50.0.38.245|50.0.38.245]] 01:58, 15 November 2012 (UTC)

:::Please don't edit others' comments on talk pages; it's considered quite rude. On a talk page, discourse is meant to be conducted, by editors for the betterment of the article. For constructive discourse to occur, a person's words must be left in tact. The act of censorship hurts the common goal of betterment. Per [http://en.wikipedia.org/wiki/Wikipedia:Talk_page_guidelines#Editing_comments Wikipedia], the authoritative source on how a wiki works best: "you ''should not'' edit or delete the comments of other editors without their permission." [[User:Lcarsos|lcarsos]]<span title="I'm an admin. I can help.">_a</span> ([[User talk:Lcarsos|talk]]) 17:38, 13 November 2012 (UTC) <small>Note: much of this conversation has been removed at the request of the authors.</small>

I think the explanation is wrong or otherwise lacking in its explanation: The P-value is not the entire problem with the frequentist's viewpoint (or alternatively, the problem with the p-value hasn't been explained). The Frequentist has looked strictly at a two case scenario: Either the machine rolls 6-6 and is lying, or it doesn't rolls 6-6 and it is telling the truth. Therefore, there is a 35/36 probability (97.22%) that the machine is telling the truth and therefore the sun has exploded. The Bayesian is factoring in outside facts and information to improve the accuracy of the probability model. He says "Either the machine rolls 6-6 (a 1/36 probability, or 2.77%) or the sun has exploded (an aparently far less likely scenario). Given the comparison, the Bayesian believes it is MORE probable that the machine rolled 6-6 than the sun exploded, given the relative probabilities. If the latter is a 1 in a million chance (0.000001%), it is 2,777,777 times more likely that the machine rolled 6-6 than the sun exploded.
To borrow a demonstration/explanation technique from the Monty Hall problem, if the machine told you a coin flip was heads, that would be 50% chance of occuring while a 2.7% chance of the machine lying, the probabilities would clearly suggest that the machine was more likely to be telling the truth. Whereas if the machine said that 100 coin flips had all come up heads (7.88x10^-31%). Is it more likely that 100 coin flips all came up heads or is it more likely the machine is lying? What about 1000 coin flips? or 1,000,000? I think the question is, whether one could assign a probability to the sun exploding. Also, I think they could have avoided the whole thing by asking the machine a second time and see what it answered. [[User:TheHYPO|TheHYPO]] ([[User talk:TheHYPO|talk]]) 19:09, 12 November 2012 (UTC)

Another source of explanation: http://stats.stackexchange.com/questions/43339/whats-wrong-with-xkcds-frequentists-vs-bayesians-comic --[[User:JakubNarebski|JakubNarebski]] ([[User talk:JakubNarebski|talk]]) 20:12, 12 November 2012 (UTC)

The P-value really has nothing to do with it. If I think that there is a 35/36 chance that the sun has exploded, then I should we willing to take any bet that the sun has exploded with better than 1:35 odds. For example, if someone bets me that the sun has exploded in which they will pay me $2 if the sun has exploded and I will pay them $35 if it hasn't, then based on my belief that the sun has exploded with 35/36 probability, then my expected value for this bet is 2*35/36 - 35 * 1/36 = 35/36 dollars and I will take this bet. Clearly I would also take a bet with 1:1 odds - my estimated expected value in the proposed bet in the comic would be 50*35/36 - 50 * 1/36 = $49 (approximately), and I would for sure take this bet. The Bayesian on the other hand has a much lower belief that the sun has exploded because he takes into account the prior probability of the sun exploding, so he would take the reverse side of the bet. The difference is that the Bayesian uses prior probabilities in computing his belief in an event, whereas frequentists do not believe that you can put prior probabilities on events in the real world. Also note that this comic has nothing to do with whether people would die if the sun went nova - the comic is titled "Frequentists vs Bayesians" and is about the difference between these two approaches. {{unsigned|171.64.68.120}}

The Labyrinth reference reminds me of an old Doctor Who episode (Pyramid of Mars), where the Doctor is also faced with a truthful and untruthful set of guards. Summarized here: http://tardis.wikia.com/wiki/Pyramids_of_Mars_(TV_story) [[User:Fermax|Fermax]] ([[User talk:Fermax|talk]]) 04:49, 14 November 2012 (UTC)

This is actually an example of the [https://en.wikipedia.org/wiki/Base_rate_fallacy Base rate fallacy]. --[[Special:Contributions/71.199.125.210|71.199.125.210]] 04:04, 19 November 2012 (UTC)

People have gone over this already, but just to be a bit more explicit:
Let NOVA be the event that there was a nova, and let YES be the event that the detector responds "Yes" to the question "Did the sun go nova?"
What we want is P(NOVA|YES)=P(YES|NOVA)*P(NOVA)/P(YES)
Suppose P(NOVA)=p is the prior probability of a nova.
Then P(YES|NOVA)=35/36, P(NOVA)=p, and P(YES)=p*35/36+(1-p)*1/36=1/36+34/36
So then P(NOVA|YES)=35p/(1+34p). If p is small, then P(NOVA|YES) is also small. In particular, the Bayesian statistician wins his bet at 1:1 odds if p<1/36, which is probably the case.
If the Bayesian statistician wants 95% confidence that he'll win his bet, then he needs p<1/666. =P

It's cute to attempt to connect this to the U.S. presidential election, but it's far likelier that it's a reference to Enrico Fermi taking bets at the Trinity test site as to whether or not the first atomic bomb would cause a chain reaction that would ignite the entire atmosphere and destroy the planet. I'll bet you $50 it is. [[Special:Contributions/71.229.88.206|71.229.88.206]] 21:29, 7 March 2013 (UTC)

I don't like the explanation at all. Some of the discussion posts give a good view on this. I'd like to share my thought about the last panel, though. The page reads as if the punch line is about the fact that you cannot spend the money if the sun was going to explode; but why does the bayesian propose this bet and not the frequentist - no reason for this. I think there is a better explanation for this panel: there are several proofs that bayesian probabilities result in "rational" behaviour: They state that if you act according to bayes' rule you cannot be cheated in betting. [[Special:Contributions/108.162.254.179|108.162.254.179]] 17:11, 6 March 2014 (UTC)

The last panel may refer to Nate Sliver's view expressed in his book {{w|The Signal and the Noise}} that if one believes one's prediction to be true one should be confident to bet on it. --[[User:Troy0|Troy0]] ([[User talk:Troy0|talk]]) 18:46, 6 July 2014 (UTC)

Please excuse my ignorance, but how is two sixes rolled on fair dice 31/32? (In the explanation: "the detector is telling the truth (31 in 32)") --[[User:Pudder|Pudder]] ([[User talk:Pudder|talk]]) 17:06, 9 December 2014 (UTC)
:Just a missreading, not stupid. The detector is telling the truth when you dont role 2 sixes. roling 2 sixes is 1/6 * 1/6 or 1/36. So not roling is 35 in 36, wait oops 36 not 32, thanks. [[Special:Contributions/108.162.216.209|108.162.216.209]] 17:39, 9 December 2014 (UTC)

I have always thought that the suggested Bet is also a reference to the Dutch Book argument for judging and accounting for probabilities underlying Bayesian interpretations of probability theory. [[Special:Contributions/141.101.98.100|141.101.98.100]] 22:11, 12 August 2015 (UTC)

The likelyhood of a solar explosion may be wrong. Since the detector I'd only used at night, the event is twice as likely to occur than listed. That said, there's a 50% chance of the event never being detected, so I'm not sure. Any one more knowledgeable than I care to comment? [[User:Mikemk|Mikemk]] ([[User talk:Mikemk|talk]]) 06:47, 5 April 2016 (UTC)

Huh. I thought that the last panel was pragmatism: "If the sun goes nova, $50 doesn't matter; I'll be dead. If the sun hasn't, I get $50!"
:Same, but sign your comments, [[User:Netherin5|Netherin5]] ([[User talk:Netherin5|talk]]) 14:09, 22 February 2019 (UTC)

This comic hurts my head. [[Special:Contributions/173.245.54.7|173.245.54.7]] 21:44, 12 August 2019 (UTC)

It is my feeling that sloppy or machiavellian academics have come to use the term "Bayesian" to mean something more like "we adjusted it to what we felt was most reasonable", which introduces so much bias that it actually leaves one unable to determine the scientific validity of the results. I was reading [https://academic.oup.com/beheco/article/23/3/619/224216 a publication], today, that made me think of that and look up this comic. —[[User:Kazvorpal|Kazvorpal]] ([[User talk:Kazvorpal|talk]]) 21:57, 11 November 2019 (UTC)

Is there a statistical angle I'm missing to the final part of the mouseover text 'did your brain fall out? [roll] yes...' Or is is purely linguistic between literal and figurative i.e. if his brain has fallen out as in he has made a careless error, then that's true. If it's literally did his brain fall out, is the 'yes' the 97% chance that it's talking about his mistake, or the ~3% chance that it's lying about the literal truth? [[Special:Contributions/172.69.69.244|172.69.69.244]] 14:46, 3 December 2019 (UTC)

2211: Hours Before Departure

2019-10-04T18:54:23Z

172.69.69.244: /* Explanation */ Better Wikipedia link

{{comic
| number = 2211
| date = October 4, 2019
| title = Hours Before Departure
| image = hours_before_departure.png
| titletext = They could afford to cut it close because they all had Global Entry.
}}

==Explanation==
{{incomplete|Created by a LATE UP-GOER 5. Please mention here why this explanation isn't complete. Do NOT delete this tag too soon.}}

Catching transportation from one place to another requires being there and being prepared before the vehicle leaves. Some transportation, such as public city buses and personal cars require very little in preparation, and one can leave as soon as the vehicle is there and ready. Others have more complications involved, whether it be in payment, security, slower boarding, etc.

To board a Greyhound bus, for example, one would normally need to be there 10-15 minutes before it is scheduled to leave, because it takes time to get everyone on board as the same time, stow luggage, and present a boarding pass or proof of payment.

Boarding an airline is even more complicated (security checkpoints, long terminal walks, more bags, etc.) making the delays longer, and so conventional advise is to arrive two hours early for a domestic (same country) flight and three hours for an international flight. Seasoned travelers can often cut these times shorter, but to be ready for unexpectedly long delays, the less experienced traveler would want to leave extra time.

Based on that, the exceedingly complicated business of travel to space would instinctively require you to be ready much longer than the three hours they recommend for international flights, however three hours is about how long it took for the astronauts traveling to the moon for the first time to prepare to take off.

The title text is a pun on the words "global entry". Global Entry is a United States Customs and Border Protection program that allows US citizens to quickly proceed through customs checks when arriving from overseas, instead of waiting in a long line to present a passport. In the case of the Apollo astronauts, their return to the earth involved re-entry into the atmosphere (technically called {{w|Atmospheric entry}}), and of course global is another word for things relating to the earth. So the Apollo astronauts could be said to have undergone "global entry" on their return. As befits a pun, the joke actually doesn't make sense, since both the Global Entry program and re-entry from space relate to returning from a trip, while the rest of the comic relates to how early you arrive to depart on a trip.

==Transcript==
{{incomplete transcript|Do NOT delete this tag too soon.}}
First panel shows a time of 6:27 A.M. and "Crew departs for launch site"
Pictured are three astronauts with helmets getting into a NASA van.

Second panel shows a time of 9:32 A.M. and "Liftoff"
Depicted is a rocket, in the process of a space launch.

The text under the panels reads, "I know I tend to arrive too early at the airport, but it still weirds me out that Neil Armstrong left for the launch site just three hours before departure.

The hover text reads, "They could afford to cut it close because they all had Global Entry."

{{comic discussion}}

Talk:2037: Supreme Court Bracket

2018-08-24T15:19:36Z

172.69.69.244:

Came here for insight, only to discover this is tomorrow's comic, I'm viewing Friday's comic on Thursday after midnight. D'oh! Damn, seeing a comic early and I can't provide or contribute to the explanation, LOL! I realize the bracket and "Sweet 16" are sports things, I think football and/or basketball, and I spotted the famous name Roe vs. Wade, so seems like court cases, but that's it. Looking forward to people explaining the smaller jokes (I spotted "Loving" and "Virginia", and I feel like I recall their license plates say "Virginia Is For Lovers" I think, I expect something there). [[User:NiceGuy1|NiceGuy1]] ([[User talk:NiceGuy1|talk]]) 04:58, 24 August 2018 (UTC)
:Protip: Thursday after midnight is Friday! Nonetheless this comic was released at 0:00 EDT meaning it was still Thursday at time zones westwards. --[[User:Dgbrt|Dgbrt]] ([[User talk:Dgbrt|talk]]) 07:03, 24 August 2018 (UTC)
:I got here at like 9:10 Pacific time and the comic was already up; normally I have to wait until like 1 AM before Randall posts it/you guys auto-mirror it.[[Special:Contributions/172.68.189.235|172.68.189.235]] 08:23, 24 August 2018 (UTC)
::The pages here are created automatically less than two minutes after the original was published on xkcd. Today, like some others in the recent past, this happened at 4:01 UTC (or GMT - the server time) which corresponds to 0:01 EDT (Randall time) and 21:01 PDT (the day before at your time.) The weekday is defined by Randall's time zone - US citizens should know about the shift from east to west. --[[User:Dgbrt|Dgbrt]] ([[User talk:Dgbrt|talk]]) 12:01, 24 August 2018 (UTC)

Errm. You can go back to the previous comic if you hit the [<Prev] button just above the current one. {{unsigned ip|141.101.107.36}}

I agree that this is a sports reference, but can someone also include some sort of note about the title? I think that the "Supreme COURT" is referring to a basketball COURT, connected to how brackets like this are used in basketball like with March Madness. [[User:B. A. Beder|B. A. Beder]] ([[User talk:B. A. Beder|talk]]) 05:50, 24 August 2018 (UTC)
:No, I'm pretty sure it's titled Supreme Court Bracket because the bracket consists of cases in which the Supreme Court of the United States made the rulings. [[Special:Contributions/162.158.90.6|162.158.90.6]] 10:35, 24 August 2018 (UTC)

Well, how would the tournament turn out? We know who won the cases, so who's the king of the US legal system? --[[Special:Contributions/162.158.90.66|162.158.90.66]] 06:41, 24 August 2018 (UTC)
: Many participants fail to reappear for the round 2, so not much progress yet. [[Special:Contributions/141.101.77.86|141.101.77.86]] 13:24, 24 August 2018 (UTC)

Moral of the story: If you are the respondent in a landmark case, you might as well give up. --[[User:Troy0|Troy0]] ([[User talk:Troy0|talk]]) 07:53, 24 August 2018 (UTC)
:I noticed that as well. Do most "landmark" cases go to the plaintiff or is this just an outlier sample?[[Special:Contributions/172.68.189.235|172.68.189.235]] 08:23, 24 August 2018 (UTC)
: But Marbury actually won the case, the court was unable to deliver the ruling [[Special:Contributions/162.158.155.104|162.158.155.104]] 09:42, 24 August 2018 (UTC)
: As I see it (IANAL), the plaintiff goal in the Supreme Court usually is to change something (overrule a previous court decision, repeal a law), while the respondent typically fights to keep things the same. If the plaintiff loses, no changes are made. If nobody sees any changes in the country, why the case would be a landmark? Only when both outcomes change things for many people, like in the Dred Scott case, the respondent win makes a landmark. [[Special:Contributions/141.101.77.86|141.101.77.86]] 13:24, 24 August 2018 (UTC)

;Adding an image
I created an image showing the winners superimposed on the original comic so you can see who is due to "play" each other next. Is there any way to upload the file? the image is this: http://www.explainxkcd.com/wiki/index.php/Special:UploadStash/thumb/15zj3hymeul4.6wctza.13964.png/600px-15zj3hymeul4.6wctza.13964.png [[User:Mrdownes|Mrdownes]] ([[User talk:Mrdownes|talk]]) 11:27, 24 August 2018 (UTC)
:In general we don't need such an image because it doesn't explain much and the winners are already highlighted at the explanation. This Wiki isn't a picture book. Nevertheless check the menu and you will find the entry "Upload file". --[[User:Dgbrt|Dgbrt]] ([[User talk:Dgbrt|talk]]) 12:09, 24 August 2018 (UTC)

The Brown won the NLRB v Brown match in round 2. (https://supreme.justia.com/cases/federal/us/380/278/) -[[Special:Contributions/172.69.69.244|172.69.69.244]] 15:19, 24 August 2018 (UTC)