explain xkcd - User contributions [en]

Talk:2295: Garbage Math

2020-04-23T07:46:07Z

172.69.54.141:

== Inclusion in Series ==
This is not a Covid19 comic. One could think that this is a comment on the difficulties of modeling the corona virus outbreak, but since discussions of exponential functions are only a small part in the comic I believe it is just a general comment on floating point arithmetic mixed in with statistical considerations. --[[Special:Contributions/108.162.229.242|108.162.229.242]] 17:28, 17 April 2020 (UTC)
:I disagree that this is not a COVID-19 comic. I also believe the one about visualizing large numbers was COVID-19 related. On the other hand, I like the idea that Randall might produce exactly 19 comics related to SARS CoViD 2019, so I'm prepared to concede the point for the sake of arbitrary numerological appeal.
:[[User:ProphetZarquon|ProphetZarquon]] ([[User talk:ProphetZarquon|talk]]) 18:42, 17 April 2020 (UTC)
::I think Exa-Exabyte was a real stretch (the virus doesn't even have DNA), but there is a tenuous link so whatever. The idea that ''this'' comic is related, on the other hand, stretches past the breaking point. There's hardly anything that can't be linked to global events if we try hard enough, but that doesn't mean there's an actual link. Sometimes a comic about garbage math is just a comic about garbage math. [[Special:Contributions/172.69.71.58|172.69.71.58]] 19:33, 17 April 2020 (UTC)
:::I think this one's much more likely to be a coronavirus comic than Exa-Exabyte was. There's an awful lot of COVID data, much of it either very imprecise or outright garbage; and the comic directly before this one ([[2294]]) involved bad modeling of said COVID data, so clearly COVID data (and its limitations) is something Randall's currently thinking of and drawing comics about. [[User:Pelosujamo|Pelosujamo]] ([[User talk:Pelosujamo|talk]]) 20:25, 17 April 2020 (UTC)
::::Exa-Exabyte was centered around biology, which gives reason to believe it was covid19 related. This one seems much more uncertain. Any conclusion that it is related is based on garbage. Jokes aside, It seems like much more of a stretch to me. Randall thinking in those terms is a reasonable argument, but personally I am going to assume this is the chain breaker unless a direct reference is made in the next couple comics since ending at 19 is would be appropriate. [[Special:Contributions/172.69.70.209|172.69.70.209]]
:: While this comic has no ''direct'' reference to Covid-19 it does appear that the math might be related. At this point we can't know if the series has ended. As such I've edited the paragraph in the explanation to identify the known ambiguities. And now I realize I've made an explanatory paragraph about "knowledge error bars" in the explanation of a comic about numerical error bars.[[User:Iggynelix|Iggynelix]] ([[User talk:Iggynelix|talk]]) 14:42, 18 April 2020 (UTC)
:::No. The reason it appears the math might be related is ''because the math relates to everything, everywhere''. That's not enough of a connection. During this pandemic, there will be a lot of comics related to the coronavirus, many of them in a row, but that doesn't mean that every comic that could be tangentially related if you squint just right should qualify as a COVID-19 comic (I ''still'' think Exa-Exabyte doesn't). There needs to be a real link, because just about ''anything'' could be twisted into a relation if you try hard enough. As a test, I hit [[Special:Random]] and got [[346: Diet Coke+Mentos]]. Wouldn't you know, that's a coronavirus comic! The father, you see, actually had COVID-19 and died, but Diet Coke and Mentos has brought him back! No. The line should be drawn here. The streak has ended. [[Special:Contributions/172.69.68.197|172.69.68.197]] 17:02, 18 April 2020 (UTC)
::::I agree this is not a serious contender for inclusion as a COVID comic. Although I'm pretty sure Randall has input to COVID19 models as garbage on his mind. But there is nothing in this comic that suggest this math be used on a pandemic. The exa byte is a different story as it is about how much of biology we cannot know or control in the midst of a lot of comics about some new biology we do not control. I do not expect that this will end the covid19 series, but I will consent that even if the next comic is a clear corona comic, it will no longer be an unbroken streak. Anyway the real streak ended at the end of March with the late April Fool's comic. I also do not at all think that the coke mentos could be seen as a COVID19 comic, that is just bulls**t trying to prove a point that I believe you fail completely. I also tried random comic (I like the idea) and found [[1208: Footnote Labyrinths]]. It is a scientific paper (with nested footnotes) and given science, we could say it was about science about Corona. Naah. But for the same reason this comic should not be considered corona. --[[User:Kynde|Kynde]] ([[User talk:Kynde|talk]]) 20:53, 18 April 2020 (UTC)

:::::I am pretty sure this IS related. Right now, everybody and his grandmother is staring at the Johns Hopkins Coronavirus numbers for different countries. Entire newspaper articles are written about these numbers and about why one country is apparently faring better than the other and what this means. The numbers are made into fancy graphics. People use these numbers to calculate fatality rates and cure rates. Politicians might even use these numbers to make decisions.
:::::And all this even though everybody KNOWS that the numbers cannot really be compared from one country to the other, because testing prerequisites vary, testing availability varies, testing procedures vary, criteria used to include a death as a coronavirus death vary. The sources of the numbers are very different and might not always be reliable. [Apparently, they include local language newspapers, website and even social media accounts. How many people DOES the Johns Hopkins University have to track all these sources reliably, worldwide, in local languages?] And not to forget some countries probably are downright lying.
:::::And still, people are comparing. I've read articles where the author admits the numbers are probably garbage in one sentence and then STILL goes on to calculate fatality rates from them in the next sentence. So, most PROBABLY related.

::::::I challenge you to find a comic in the archive that can't be twisted to say it's related to COVID-19. At this point people are finding connections in the same way that people analyze "the curtain is blue". [[Special:Contributions/108.162.245.26|108.162.245.26]] 22:06, 19 April 2020 (UTC)
--[[Special:Contributions/141.101.69.153|141.101.69.153]] 21:53, 19 April 2020 (UTC)

This comic very much reminds me of this article: [https://www.realclearmarkets.com/articles/2020/04/17/its_decidedly_not_the_math_its_always_people_489344.html
It's Decidedly Not the Math. It's Always People] So much so that my first thought was that the comic was inspired by it, though of course I can't prove it.[[User:BrianZ|BrianZ]] ([[User talk:BrianZ|talk]]) 00:52, 20 April 2020 (UTC)

== Math and Error bars ==

Well this is surprising came here thinking I understood it just to see what the discussion looked like. Ended up learning something new. I was able to understand intuitively the comic. But this is my first exposure to actually doing math on the error bars. I think I was supposed to do that in college but I don't remember anyone ever explaining how it should work. --[[Special:Contributions/162.158.63.208|162.158.63.208]] 18:14, 17 April 2020 (UTC)

In recent days, there have been a number of math "quizzes" in this same type of format, albeit generally with only addition and maybe multiplication, appearing on Facebook. Should the explanation include a reference to this as a possible contributing reason for Randall's comic? One could also argue that those quizzes have been appearing on Facebook as a way to spend/waste time during the coronavirus pandemic lock-down, making he comic at least tangentially related to Covid19 LIES.
:: Unsigned vandalism? /\ [https://www.explainxkcd.com/wiki/index.php?title=Talk:2295:_Garbage_Math&diff=190866&oldid=190856 change history] @user Please feel free to move your discussion to an appropriate forum and remove both the edit and this comment at such time. [[User:Iggynelix|Iggynelix]] ([[User talk:Iggynelix|talk]])

What's the difference between relative error and absolute error? I don't understand these terms. Maybe add?
: Absolute error is the amount of uncertainty in a value measured as a given number. e.g. 5.7 ± 1.2 means that actual value lies somewhere between 5.7 - 1.2 and 5.7 + 1.2 = 4.5 to 6.9. If you change the 5.7 to another value, you still get the same absolute difference of maximum and minimum values. Relative error depends on the value you are comparing to. e.g. 5.7 ± 10% would be between 5.7 - 0.57 and 5.7 + 0.57 = 5.13 to 6.27. The absolute difference of maximum and minimum would change if the main number changes. e.g. 11.3 ± 10% would be between 10.17 and 12.43, which has a greater absolute difference of maximum and minimum than the previous example. [[User:Nutster|Nutster]] ([[User talk:Nutster|talk]]) 01:54, 18 April 2020 (UTC)

Are all of these equations consistent with garbage = infinity?
: Unfortunately, as written, these equations would not make sense by defining Garbage as an infinity. Infinity is not a number you can count to or measure in between integers. Infinity is the idea of unending-ness. Trying to use infinity as if it a finite number yields all sorts of invalid results. In this case Garbage is defined as an arbitrary finite number with a large amount of uncertainty in its value. [[User:Nutster|Nutster]] ([[User talk:Nutster|talk]]) 01:40, 18 April 2020 (UTC)
::: That's a pretty good definition of 'garbage' in ''any'' case, plus or minus 10%. ( See also [https://www.weforum.org/agenda/2017/06/landfill-mining-recycling-eurelco/ valuable garbage]) [[User:Iggynelix|Iggynelix]] ([[User talk:Iggynelix|talk]]) 14:19, 18 April 2020 (UTC)

Would the summation divided by ''n'' just give you the arithmatic mean of the data set? [[User:Nutster|Nutster]] ([[User talk:Nutster|talk]]) 01:55, 18 April 2020 (UTC)
:Pretty much, but the point is probably more that (without consistent bias across the set, just 'random' errors for each item) it suppresses the degree of garbagicity as outliers are increasingly nullified by the greater number of more competently accurate values and (if it's a symmetric error) opposing outliers. [[Special:Contributions/162.158.34.222|162.158.34.222]] 09:29, 18 April 2020 (UTC)

The statement that NaN^0 isn't fully justified and I'm not clear it belongs. [[User:Djbrasier|Djbrasier]] ([[User talk:Djbrasier|talk]]) 18:46, 18 April 2020 (UTC)
: I agree... It also isn't evident to me that this comic has anything to do with floating-point math, which is the only thing that could (even slimly) justify its inclusion. This is about statistics, not programming. --[[Special:Contributions/108.162.215.12|108.162.215.12]] 05:25, 19 April 2020 (UTC)

I'm concerned that, with "Precise Number" there's the usual confusion between Accuracy and Precision (''edit: and of course Resolution, too!''). A precise number can still be utter garbage, as 84.7489327(646475)% of all mathematicians could tell you. [[Special:Contributions/162.158.111.241|162.158.111.241]] 13:59, 19 April 2020 (UTC)
:The table of formulae for the propagation of variance σ addresses that aspect. You can't know the accuracy of a result without knowing the precision of its calculation, and while reducing precision always reduces accuracy, it's not the other way around. But precision is inherent in the representation and operations, while accuracy is secondary when you aren't discussing the initial measurements of the inputs, so I think the terminology is correct.
:By the way, shout out to [https://www.explainxkcd.com/wiki/index.php?title=2295%3A_Garbage_Math&type=revision&diff=190882&oldid=190870 172.68.51.124] for filling out all but one of those table entries. I wonder where they looked them up. I'm guessing a ''CRC Handbook'' left over from High School chemistry or some such? Anyway, good job! This really looks classy now that it's been cleaned up a bit. [[Special:Contributions/162.158.255.64|162.158.255.64]] 06:45, 20 April 2020 (UTC)

Could someone please double check that the given uncertainty formula for "Precise number / ( Garbage – Garbage )" at the second to the bottom is correct? I'm not sure it properly accommodates the uncertainty of the numerator. [[Special:Contributions/162.158.255.64|162.158.255.64]] 07:48, 20 April 2020 (UTC)

Are the [https://www.explainxkcd.com/wiki/index.php?title=2295:_Garbage_Math&diff=191031&oldid=191030 changes from "=" to "≈"] correct? Either way, isn't the proper symbol for the relation "≅" ("approximately equal to") instead of "≈" ("almost equal to")? As is illustrated by catastrophic cancellation, an approximation may not be "almost" correct. But my question is, aren't those relations to the resulting standard deviation exact instead of approximate? [[Special:Contributions/172.69.22.152|172.69.22.152]] 04:16, 22 April 2020 (UTC)
:The formulas are the first approximation for small sigma. They are exact for a linear combination of the random variables in the term. With rising sigma, higher order terms can get relevant. Sebastian --[[Special:Contributions/172.69.54.141|172.69.54.141]] 07:46, 23 April 2020 (UTC)

Talk:2167: Motivated Reasoning Olympics

2019-06-25T08:25:38Z

172.69.54.141:

Reminds me of the Monty Python Argument Clinic :) [[User:Hawthorn|Hawthorn]] ([[User talk:Hawthorn|talk]]) 16:50, 24 June 2019 (UTC)

It certainly DOESN'T remind you of the Monty Python Argument Clinic, you gormless git! [[Special:Contributions/162.158.214.28|162.158.214.28]] 17:46, 24 June 2019 (UTC)
:Yes it DOES![[Special:Contributions/141.101.105.192|141.101.105.192]] 17:57, 24 June 2019 (UTC)
::No it doesn’t.
:::You're just being contrary. [[Special:Contributions/162.158.214.136|162.158.214.136]] 20:14, 24 June 2019 (UTC)
::::No I'm not. [[Special:Contributions/172.69.54.141|172.69.54.141]] 08:25, 25 June 2019 (UTC)

== Explain "Motivated Reasoning"? ==

Shouldn't the explanation include some contextual explanation of "[https://en.wikipedia.org/wiki/Motivated_reasoning Motivated Reasoning]" as pertaining to Cueball's behavior shown in the comic?
https://en.wikipedia.org/wiki/Motivated_reasoning
[[User:ProphetZarquon|ProphetZarquon]] ([[User talk:ProphetZarquon|talk]]) 20:37, 24 June 2019 (UTC)

: I added a Wikipedia link to Motivated Reasoning in the title text explanation earlier, but I'm wondering if some of that detail should be moved earlier in the explanation. [[User:Ianrbibtitlht|Ianrbibtitlht]] ([[User talk:Ianrbibtitlht|talk]]) 23:10, 24 June 2019 (UTC)

== Better quality images? ==

This probably isn't the right place but I figured this would get the most visibility. I noticed that the image here made it really hard for me to see the "2" engraved on the trophy, but the image on xkcd.com was much clearer. Yada yada yada, turns out there's much higher quality images on xkcd.com for all comics starting with [[1084]], for example for this comic:

https://imgs.xkcd.com/comics/motivated_reasoning_olympics.png is the normal image,

https://imgs.xkcd.com/comics/motivated_reasoning_olympics_2x.png is the higher resolution image.

Shouldn't the wiki start using the higher quality images?

--[[User:NeatNit|NeatNit]] ([[User talk:NeatNit|talk]]) 17:53, 24 June 2019 (UTC)

: While there is a higher quality image available on the XKCD site, it's not the one displayed on the comic on xkcd.com. The same lower-quality image is displayed on both sites by default. [[User:Ianrbibtitlht|Ianrbibtitlht]] ([[User talk:Ianrbibtitlht|talk]]) 18:44, 24 June 2019 (UTC)

:: I am seeing the higher-quality image on xkcd.com. I guess it has to do with screen DPI. The HTML on xkcd.com is:
:: <pre><img src="//imgs.xkcd.com/comics/motivated_reasoning_olympics.png" title="..." srcset="//imgs.xkcd.com/comics/motivated_reasoning_olympics_2x.png 2x"/></pre>
:: So it probably selects it automatically only when it'd be useful. This wiki doesn't, obviously, since it doesn't have the higher-quality image and, best I can tell, there doesn't seem to be a way to make a template do this.

:: I'm trying to figure this out right now on [[User:NeatNit/Template/comic]] but I can't find a way to make it display an image at half of its resolution, without me knowing its resolution in advance. I also can't find any parser function that returns an image's dimensions. So annoying. --[[User:NeatNit|NeatNit]] ([[User talk:NeatNit|talk]]) 18:52, 24 June 2019 (UTC)

:::I would expect this can't work correctly without support for srcset in mediawiki itself. -- [[User:Hkmaly|Hkmaly]] ([[User talk:Hkmaly|talk]]) 22:13, 24 June 2019 (UTC)

:I have also noticed that this wiki displays lower resolution images than the official xkcd site, when viewing at high DPI. I had previously assumed it was just a moderate resolution copy chosen to conserve explainxkcd server resources. I would love to see a higher resolution when available. [[User:ProphetZarquon|ProphetZarquon]] ([[User talk:ProphetZarquon|talk]]) 20:18, 24 June 2019 (UTC)

173: Movie Seating

2019-06-08T15:50:35Z

172.69.54.141: Grammar

{{comic
| number = 173
| date = October 20, 2006
| title = Movie Seating
| image = movie_seating.png
| titletext = It's like the traveling salesman problem, but the endpoints are different and you can't ask your friends for help because they're sitting three seats down.
}}

==Explanation==
In most movie theaters in the US, {{w|Movie_theater#Pricing_and_admission|seats are not reserved}}.<sup>[1]</sup> That is, tickets are sold by screening without seat assignment, and therefore an entering patron can take any vacant seat. Therefore, a group of incoming patrons may walk in a column and take a section of consecutive seats in a row, each person taking one next to the person in front of them. The order of these people is thus determined by the order in which they walk into the theater, which is in most cases random.

Cueball is upset at the way he and his friends have sit down at the movie theater. Part of the problem is that two people who are apparently in a relationship do not sit together. He therefore tries to use a {{w|social graph}} to calculate the best way for him and his seven friends to sit in a row, while taking into account all of the social connections among them. In {{w|mathematics}}, this type of problem is called {{w|combinatorial optimisation}}. The most popular example, the {{w|Travelling salesman problem|travelling salesman problem}}, is referenced in the title text, as well as in comics [[287]] and [[399]].

The title text shows that another part of the problem is that Cueball's friends, who could have helped him calculate a solution, are each sitting three seats away from him, and so he cannot ask them for help.

<sup>[1]</sup> Starting in 2017, certain Marcus theaters around the U.S. now sell movie tickets with reserved seats, both online and when purchased at the theater. When you buy your ticket, you also specify which seat you would like to sit in. Therefore, if you buy multiple tickets, you can select seats that are adjacent to each other, provided that you purchase them early enough before the point when you cannot find two or more empty seats together any longer.

==Solutions==
Two hypothetical solutions for the specific problem proposed in the comic are displayed:

[[File:173_Solutions.jpg]]

==Transcript==
:At the movies, I get frustrated when we file into our row haphazardly, ignoring the computationally difficulty problem of seating people together for maximum enjoyment.
:[Map of relationships between 8 people.]
:[Legend:]
::Single line: friends.
::Double line: in a relationship.
::Arrow: one-way crush.
::Dashed line: acquaintances
:[The eight friends sit in a row in a dark cinema. Cueball and one other are between two lovers.]
:Cueball: Guys! This is not socially optimal!

==Trivia==
*Randall states in xkcd: volume 0 that this was his "passive-aggressive way of asking my friends to let me plan seating."

{{comic discussion}}
[[Category:Comics featuring Cueball]]
[[Category:Comics featuring Megan]]
[[Category:Comics featuring Hairy]]
[[Category:Math]]
[[Category:Comics with inverted brightness]]
[[Category:Multiple Cueballs]]

632: Suspicion

2019-06-05T03:56:58Z

172.69.54.141: Correcting language.

{{comic
| number = 632
| date = September 4, 2009
| title = Suspicion
| image = suspicion.png
| titletext = Fine, walk away. I'm gonna go cry into a pint of Ben&Jerry's Brownie Batter(tm) ice cream [link], then take out my frustration on a variety of great flash games from PopCap Games(r) [link]
}}

==Explanation==
[[Rob]] is having online chats with what appears at first glance to be a woman. However, he grows suspicious at the apparent consumerism dedication of the "woman" - and perhaps of the perfection of the online connection, touching on the stereotypical nerd fear that any relationship going well must contain some secret flaw - and so requests that they both "get tested". The woman on the other end of the computer does not pass a {{w|CAPTCHA}} test and is unable to prove she is a human.

This is an internet version of the {{w|Turing test}}. A {{w|spambot}} is a program that sends out emails or links such as in the title text to simulate a human's writing but contains advertising. This test is called "VK", which stands for Voight-Kampff, which is an empathy test in the novel ''{{w|Do Androids Dream of Electric Sheep}}'' and film ''{{w|Blade Runner}}'', which determines human from replicant.

In using the phrase "get tested", the comic is making a joke that refers both to the CAPTCHA test above and the {{w|Sexually transmitted disease|STD or VD}} test that couples will take to make sure they are physically free of communicable diseases.

The name "Lisa" may be an allusion to {{w|ELIZA}}, one of the first chatbots, written in 1966. According to its (her?) creator, people became "quickly and deeply emotionally involved with the computer program" during the chat. "Lisa" may also reference the computer girlfriend Lisa from the 1985 movie [https://en.wikipedia.org/wiki/Weird_Science_(film) Weird Science]

The title text is the spambot's last sad goodbye — it includes lots of product advertisements and links, such as an online advertiser may insert into a search results page.

[[329: Turing Test]] is another comic dealing with Turing tests/CAPTCHAs.

==Transcript==
:[Rob is sitting at a computer, typing.]
:Rob: I've loved our online chats these past few months, Lisa.
:Computer: Me too. I really like you, Rob.

:[Rob continues to type.]
:Rob: It's just... now and then you mention products you like, and... I worry.
:Computer: What? Honey...

:[Rob types.]
:Rob: Before this goes any further, I think we should go get tested. You know, together.
:Computer: You don't trust me?
:Rob: I just want to be sure.

:[A web browser is open.]
:VK Couples Testing
:Test ID: 21871138
:Waiting...Partner connected.
:(A pair of CAPTCHA images)
:[You] Library
:[Partner] Kittens
:Rob: Okay, mine says "library". Yours?
:Computer: I... uh...
:Rob: Oh god.
:Computer: I'm more than a spambot! Our love was real!
:Rob: Goodbye, Lisa.

{{comic discussion}}
[[Category:Comics featuring Rob]]
[[Category:Romance]]