explain xkcd - User contributions [en]

3055: Giants

2025-02-24T22:10:18Z

162.158.134.38: /* Explanation */ +WP links for most terms

{{comic
| number = 3055
| date = February 24, 2025
| title = Giants
| image = giants_2x.png
| imagesize = 341x423px
| noexpand = true
| titletext = I can't get over the suspicion that all those viral pictures are photoshopped and 'Flemish' belongs in the lower right circle.
}}

==Explanation==
{{incomplete|Created by a BOT giant - Please change this comment when editing this page. Do NOT delete this tag too soon.}}

{| class="wikitable"
|-
! Name !! Class !! Explanation
|-
| {{w|Red giant|Red Giant}} || Space || A type of star
|-
| {{w|Blue giant|Blue Giant}} || Space || A type of star
|-
| Iron Giant || Space, Not Real || Title character from a {{w|The Iron Giant|1999 animated film}} and the {{w|The Iron Man (novel)|1968 children's book}} it was based on (written by English poet and author {{w|Ted Hughes}} and published outside the US as ''The Iron Man: A Children's Story in Five Nights'') : a robot from outer space.
|-
| {{w|Frost Giant (disambiguation)|Frost Giant}} || Not Real || Beings from Norse mythology (and Marvel comics)
|-
| Jolly Green Giant || Not Real || A mascot for a {{w|Green Giant|brand of canned vegetables}}.
|-
| {{w|Cardiff Giant}} || Geologic/Planetary, Not Real || An 1869 hoax
|-
| {{w|Atacama Giant}} || Geologic/Planetary || A prehistoric {{w|geoglyph}}
|-
| {{w|Paratethys#Salt Giants|Salt Giant}} || Geologic/Planetary || A huge salt deposit below the Mediterranean sea
|-
| {{w|Gas giant|Gas Giant}} || Space, Geologic/Planetary || A gaseous planet like Jupiter or Saturn
|-
| {{w|Ice giant|Ice Giant}} || Space, Geologic/Planetary || An icy planet like Uranus or Neptune
|-
| {{w|Man in the Moon|The Man In The Moon}} || Space, Geologic/Planetary, Not Real || A face visible in a crescent moon's shadow, sometimes shown as a character in children's nursery rhymes

|}

The title text refers to the {{w|Flemish Giant rabbit}}, the largest breed of domestic rabbit (about the same size as a small dog like a terrier).

==Transcript==
{{incomplete transcript|Do NOT delete this tag too soon.}}

{{comic discussion}}
[[Category:Space]]
[[Category:Astronomy]]
[[Category:Buns]]
[[Category:Fiction]]

Talk:2911: Greenland Size

2024-03-26T08:42:15Z

162.158.134.38:

Anyone else really wanting to know the radius for which the title text is true? I got [[356]]'d
[[User:Rxy|Rxy]] ([[User talk:Rxy|talk]]) 20:28, 25 March 2024 (UTC)

New life goal: Go to the poles, find the ring that is mapped to-scale, and color it. Require all satellite maps to be modified to add this stripe of color. [[User:PotatoGod|PotatoGod]] ([[User talk:PotatoGod|talk]]) 22:37, 25 March 2024 (UTC)

This is clearly based on Lewis Carroll's Sylvie and Bruno Concluded (1893) which discusses a map made at a scale of 1:1. [[User:Take The A Train To Watertown|Take The A Train To Watertown]] ([[User talk:Take The A Train To Watertown|talk]]) 22:49, 25 March 2024 (UTC)

Which latitude of Greenland is 1660miles across? I'm noodling around and can find a spot in the northern part which is - more or less - 1660*km* wide, but nothing close to that number in miles.

Hmm. First time making a comment here, thought that the title text was referencing that the Mercator projection goes to infinity at the poles, and there would be a ring where the map’s unseen parts is 1:1 to the real world.

Yeah, I think the explanation is wrong; there is a ring around the poles which is the same size on the map as it is in real life, because the mercader projection stretches it out. [[Special:Contributions/172.71.150.50|172.71.150.50]] 05:49, 26 March 2024 (UTC)

I'm amazed at how nitpickingly annoying Cueball can get with respect to mapmaking. [[Special:Contributions/162.158.134.38|162.158.134.38]] 08:42, 26 March 2024 (UTC)

821: Five-Minute Comics: Part 3

2021-05-12T12:47:23Z

162.158.134.38: /* Explanation */ Missing "of"

{{comic
| number = 821
| date = November 19, 2010
| title = Five-Minute Comics: Part 3
| image = five minute comics part 3.png
| titletext = Resulting in The Little Rock 9x + C.
}}

==Explanation==
This is the third of three "five-minute comics" Randall posted during a week in November 2010. The introduction to the comic explains everything you need to know about the circumstances behind it.

Randall obviously made more than three of these five minutes comics, and one of them was published later, for a short period of time by a mistake, but an android xkcd browser picked it up while it was on-line and saved it. Since then it has been added to explain xkcd. So here is a complete list of all four comics in the entire [[:Category:Five-minute comics|Five-minute comics]] series:
*[[819: Five-Minute Comics: Part 1]]
*[[820: Five-Minute Comics: Part 2]]
*[[821: Five-Minute Comics: Part 3]]
*[[Five-Minute Comics: Part 4]]

Here is a list with explanations for each of the small comics:
*1. {{w|Pearl Harbor}} is a US Navy base that was {{w|Attack on Pearl Harbor|attacked}} in 1941 by Japanese airplanes, which prompted the US to join World War II. The attacks were made on ''December'' 7, 1941, not November 7. Thus, Randall is correct in depicting a Navy base going about its usual business.

*2. {{w|Breastfeeding in public}} is a touchy subject in parts of the world. In the US, it is considered by some to be inconsiderate to others who would prefer not to see such a display. Of course, women breastfeeding in public are generally feeding their infants, not other adults. The situation presented in the comic is an absurd exaggeration of the debate.

*3. "s" is the command in {{w|sed}} to perform a pattern search-and-replace; the syntax has also been adopted by other text-processing utilities, including {{w|Perl}} (a favorite subject of xkcd), and has entered into the geek lexicon as something that could appear in general conversation. The specific command "s/I think that/I saw a study once that said/g" means "Find all occurrences of the phrase 'I think that', and replace it with the phrase 'I saw a study once that said'." This will, indeed, improve the persuasiveness of an article, as the existence of scientific evidence will make people more likely to believe what's said, while most people won't even think to actually look up the study in question.

*4. Arson is the crime of intentionally setting fire to a structure. {{w|Billy Joel}} will no doubt claim {{w|We Didn't Start the Fire|he didn't start the fire}}. And it turned out that they believed him. This was mentioned in the title text of [[1794: Fire]], which displays another similarly folded newspaper front page, with only the headline readable. The picture shown the fire Billy was arrested for, but he was only detained briefly. The song is also mentioned in [[1775: Things You Learn]].

*5. Coca-Cola is a fizzy cola-flavored soft drink, commonly abbreviated as "coke." {{w|Pop Rocks}} are a candy that contain tiny bubbles of gas, so that as the sugary candy dissolves on your tongue, it creates a popping sensation. For a long time, it was claimed that drinking the two together would cause one's stomach to explode; this was finally put to rest as some people (the Mythbusters in particular) started actually trying it, and discovered that it's merely painful, not lethal.
:Here, it's combined with elements of other common scary urban legends (phones ringing and creepy laughter) to form something bizarre.

*6. After ''{{w|Brown v. Board of Education}}'' ruled that schools could not segregate based on race, nine African American students from Little Rock, Arkansas enrolled in the previously-segregated Little Rock Central High School. The school board could not officially deny them attendance, but members of the community (and, after Arkansas governor Orval Faubus intervened, the Arkansas National Guard) formed a blockade to physically prevent them from entering the school building. The governor claimed this was within his power even after ''Brown v. Board'', because the students were enrolled without issue, they were just physically blocked from entering the school building. After determining that the right to enroll in a school does, implicitly, include the right to actually attend classes there, president Eisenhower ordered the 101st Airborne Division to accompany the students and force the National Guard to stand down, thus integrating the school. This incident became known as the {{w|Little Rock Nine}}.
:However, {{w|Integral|integration}} also has a meaning in mathematics. This is indicated in the comic with the soldiers lifting up a giant integral sign to place beside the school, in order to (mathematically) integrate it. Normally, an integral only makes sense on functions; however, since this is the Little Rock ''Nine'', if we take the integral of the constant function ''f''(''x'') = 9, we do, in fact, get 9''x'' + ''C'', as stated in the title text.

*7. Cell phones with advanced computing capabilities, typically at least requiring fully-featured Internet browsing, multimedia capabilities, and the ability to run software applications, are called "smartphones." Most cell phones also have a "vibrate" function that allows someone in a public situation to receive calls without alerting others; the phone will discreetly vibrate rather than activate a ringtone, thus privately notifying the owner that a call is incoming. A semi-common problem with this feature is that a vibrating phone on a table that has a slight slope will slowly - or, if the slope is bad enough, rather quickly - slide down the slope, possibly falling off the table and breaking. If our smartphones ever decided to kill us, this would possibly be their only method of attack.
**Randall later [http://what-if.xkcd.com/5/ covered this] in his [[what if?]] blog.

*8. The Three Little Pigs is a children's fairy tale about three pigs who build their houses out of, respectively, straw, sticks, and bricks. A wolf comes along and eats the pigs living in the straw and stick houses, but he can't knock down the brick house, because his only method for breaking them down is to blow on them until the material falls to pieces. (In some variants, the foolish pigs seek refuge in the brick house for a happier ending.)
:The 119 Little Pigs seems to be a variant where the pigs build their houses out of the 118 {{w|chemical elements}} (and bricks, presumably). The 38th little pig builds his house out of {{w|strontium}}, which is, of course, the 38th element on the Periodic Table. One wonders what happened to the pigs who are stuck making their houses out of elements that are gaseous or liquid at room temperature, or those whose houses would react with the air and/or undergo nuclear decay.
:In his book what if?, in the first comic, it shows the 92nd little pig, who built his house out of depleted Uranium, The wolf responded, "Dude". [https://store.xkcd.com/pages/if-you-re-looking-for-the-what-if-book/]
:Although given the water content in exhaled breath, it's {{w|Alkali metal#Reaction with water (alkali metal hydroxides)|easy to see}} how the wolf would huff, puff, and blow down the houses made of {{w|lithium}}, {{w|sodium}}, {{w|potassium}}, {{w|rubidium}}, {{w|caesium}}, and {{w|francium}}. Though making a houses out of {{w|hydrogen}}, {{w|helium}}, {{w|nitrogen}}, {{w|oxygen}}, {{w|fluorine}}, {{w|neon}}, {{w|chlorine}} and {{w|krypton}} would all be very difficult as they are gases at room temperature {{Citation needed}}. Also, there would be issues such as death from the toxicity of the elements, e.g. fluorine would kill the pig and wolf. The piggies may have difficulty collecting enough metal, as they would have trouble collecting enough {{w|technetium}} (43), which only occurs in minute traces, and {{w|astatine}}, of which approximately 1 ounce exists on earth.
:It could be a coincidence, or possibly Randall's intent, that the wolf asks "What is this shit?" while referring to strontium while "stronzo" is an Italian (vulgar) word for "turd", pronounced almost the same (it is a common source of bad taste jokes) and stront is a Dutch word for shit.

*9. "Fastest gun in the West" is a boast commonly made in Western movies, where it is used to mean that a person is the fastest at drawing his gun in a duel (or, alternatively, can fire his gun the fastest). It doesn't actually describe the gun itself, and certainly doesn't describe how fast the gun can gallop across the land.

*10. "It's what separates the ''men'' from the ''boys''" is a phrase used to describe "macho" activities that, apparently, only "real men" will participate/do well in; all the other men haven't grown up yet, and are thus "boys." {{w|Centrifuge}}s are used to rapidly separate a material from the liquid it's suspended in; this is either a pun on the word "separate", or an attempt by Randall to make the occupation of lab technician seem macho.
**In the film ''{{W|Moonraker_(film)|Moonraker}}'', {{W|James Bond}} was almost killed in a centrifuge used as a g-force training vehicle for pilots/astronauts - but he survived - and he for sure is a real man... See also [[123: Centrifugal Force]].

*11. Narnia is the mythical land in ''{{w|The Chronicles of Narnia}}''. In the books, time passes differently in Narnia, such that one can spend many years in Narnia and come out to find that almost no time at all has passed on Earth; conversely, during a short trip back to Earth, hundreds of years could pass in Narnia. {{w|Lucy Pevensie|Lucy}} is taking advantage of this by putting a computer in Narnia to perform extremely fast computation. {{w|Folding@home}} and {{w|SETI@home}} are distributed computing projects that aim to solve extremely large computational problems by pooling together computer resources of thousands of home computers who volunteer for the project; Folding@home looks at how proteins are folded, which has applications in medical science, and SETI@home analyzes EM waves from space, looking for signs of extraterrestrial intelligent life amongst the cosmic background noise. Running through all of that data in a few hours would be quite an accomplishment indeed, given that, as Peter points out, the idea has many problems Lucy has evidently overcome:
**The book was written in 1957 and it occurs even earlier than that, long predating personal computers, so Lucy shouldn't even have one.
**Even if it occurs in an alternate universe where the PC was invented before 1957, the storage that would be needed to store the entire Folding@home and SETI@home databases would be far beyond her means, since the characters in the book are evacuees who don't have any money.
**Even if she somehow pulled that much storage space together, the time needed for one computer to run through those databases is on the order of millennia. A computer would not continuously run for that long without careful treatment, which Narnia is not equipped for.
**Even if we handwave around that issue (''"Aslan, use your power to keep all dust away from this computer for the next ten thousand years, please"''), the wall socket powering the computer is on the Earth side. Mains power outlets in the UK provide alternating current with an amplitude of 230 volts and a frequency of 50 hertz. The 50 Hz part is what's important here: all devices designed to work with UK mains power expect a 50 Hz sine wave. The time difference between Earth and Narnia would substantially elongate the sine wave in a method similar to the Doppler effect, which would probably prevent the computer from functioning at all. The frequency issue can be avoided by converting the alternating current to direct current on earth and passing the direct current to Narnia. However, to have a usable amperage (coulombs per second) on Narnia, the amperage (coulombs per second) on earth would have to be absurdly high, requiring wires much larger than shown. Also, the electricity costs would be too high.
**The time differential doesn't occur while people are entering/exiting Narnia (though they do occur while the wardrobe's open) or the Pevensie children would have had had some difficulty surviving the transition. Since the cables of the computer are crossing between the worlds, it seems unlikely that the time differential is even active yet.
:See also: [[1786: Trash]]

*12. ''{{w|The Honeymooners}}'' is a classic American sitcom. The show stars Ralph and Alice Kramden, and Ralph frequently makes empty threats of the form "One of these days, Alice...," followed by a combination of onomatopoeia. For example: "One of these days, Alice... BANG! ZOOM! Straight to the moon!" (Alice inevitably replies "Ahhh, shut up.")
:Here, Randall takes the pattern to a ridiculous and not-at-all threatening place.

==Transcript==
:Because of a family illness, instead of regular comics, this week I'll be sharing some strips that I drew as part of a game I played with friends. Each comic had to be written and drawn in five minutes.

:--Randall

:;Comic #1
:Pearl Harbor. November 7th, 1941.
:[There is a beach, with some ships floating in a crescent shaped harbor.]

:[The same bay, again.]

:[The boats continue to move about the harbor.]

:[The boats do their thing. A title explains.]
:(We're going to be here a while, since the attack wasn't until December.)

:;Comic #2
:[Cueball is sitting on a bus, Megan in front of him. Another person is sitting in front of Megan and another person is sitting behind Cueball.]
:I know it's natural and all, but I really wish women on the bus wouldn't try to breastfeed me.
:Megan: C'mon, have some milk. Right here.
:Cueball: I'm ''reading''.

:;Comic #3
:s/I think that/I saw a study once that said that/g
:Instant persuasiveness multiplier!

:;Comic #4
:[A newspaper front page. Billy Joel is between two policemen.]
:Times
:Billy Joel Arrested for Arson

:;Comic #5
:[One person has a cord leaving their mouth, the other is holding a handset on the end of it to their ear.]
:Handset: Hee hee hee... *giggle*
:I hear that if you drink coke and eat pop rocks, you vomit up a corded telephone handset on which you hear creepy little girls giggling.

:;Comic #6
:[Three soldiers are holding a large integral sign, while a fourth points a gun at the Little Rock High School.]
:1957: Eisenhower orders the military to integrate Little Rock High School.

:;Comic #7
:[A smartphone is vibrating across a table, towards a person.]
:The smartphones got ''too'' smart... and developed a taste... for BLOOD!
:Fortunately, the only way they could move was by turning on their vibrate while on a sloped table.

:;Comic #8
:[Cueball is reading to his child.]
:Cueball: And the wolf went to see the 38th little pig, who had built his house out of strontium.
:Cueball: And the wolf was all, "Ok, what is ''with'' this shit?"
:The 119 Little Pigs

:;Comic #9
:[Cueball is holding up a gun.]
:Cueball: Fastest gun in the west!

:[The gun is galloping across the desert.]
:''gallop gallop''

:[There is a podium, with a gun in each position.]
:Winner!

:;Comic #10
:[A picture of a centrifuge dominates the panel.]
:Centrifuges: They're what separate the men from the boys.

:;Comic #11
:[A computer monitor is plugged in, and cables run into a wardrobe.]
:Lucy: Time passes differently in Narnia, so by putting the CPU and storage for my machine there, I was able to run through the Folding@Home and Seti@Home databases in about an hour.
:Peter: There are so many problems with that.

:;Comic #12
:[Someone is talking to Alice.]
:Person: One of these days, Alice... Wham, zoom, sploosh, fwoom, splash, gurlle, wheeeee, fwoosh, aren't waterslides fun?!

==Trivia==
*A T-shirt based on the "Centrifuges" strip is available in the [https://store.xkcd.com/products/centrifuge xkcd store].

{{comic discussion}}

[[Category:Five-minute comics| 03]]
[[Category:Comics sharing name|Five-minute comics]]
[[Category:Comics featuring Cueball]]
[[Category:Comics featuring Megan]]
[[Category:Substitutions]]
[[Category:Chronicles of Narnia]]
[[Category:Puns]]
[[Category:Multiple Cueballs]]
[[Category:Comics with xkcd store products]]
[[Category:Smartphones]]
[[Category:Analysis]]

882: Significant

2021-04-17T12:38:57Z

162.158.134.38: /* Explanation */ dice -> die

{{comic
| number = 882
| date = April 6, 2011
| title = Significant
| image = significant.png
| titletext = So, uh, we did the green study again and got no link. It was probably a-- "RESEARCH CONFLICTED ON GREEN JELLY BEAN/ACNE LINK; MORE STUDY RECOMMENDED!"
}}

==Explanation==
This comic is about {{w|data dredging}} (aka ''p''-hacking), and the misrepresentation of science and statistics in the media. A girl with a black ponytail comes to [[Cueball]] with her claim that {{w|jelly beans}} cause {{w|acne}} and Cueball then commission two scientists (a man with goggles and [[Megan]]) to do some research on the link between jelly beans and acne. They find no link, but in the end the real result of this research is bad news reporting!

First some basic statistical theory. Let's imagine you are trying to find out if jelly beans cause acne. To do this you could find a group of people and randomly split them into two groups - one group who you get to eat lots of jelly beans and a second group who are banned from eating jelly beans. After some time you compare whether the group that eat jelly beans have more acne than those who do not. If more people in the group that eat jelly beans have acne then you might think that jelly beans cause acne. However, there is a problem.

Some people will suffer from acne whether they eat jelly beans or not and some will never have acne even if they do eat jelly beans. There is an element of chance in how many people prone to acne are in each group. What if, purely by chance, all the group we selected to eat jelly beans would have had acne anyway while those who didn't eat jelly beans were the lucky sort of people who never get spots? Then, even if jelly beans did not cause acne, we would conclude that jelly beans did cause acne. Of course it is very unlikely that all the acne prone people end up in one group by chance, especially if we have enough people in each group. However, to give more confidence in the result of this type of experiment, scientists use statistics to see how likely it is that the result they find is purely by chance. This is known as {{w|statistical hypothesis testing}}. Before we start the experiment, we choose a threshold known as the significance level. In the comic the scientists choose a threshold of 5%. If they find that more of the people who ate jelly beans had acne and the chance it was a purely random result is less than 1 in 20, they will say that jelly beans do cause acne. If however, the chance that their result was purely by random chance is greater than 5% they will say they have found no evidence of a link. The important point is this – '''there could still be a 1 in 20 chance that this result was purely a statistical fluke'''.

At first the scientists do not want to stop playing the addictive game ''{{w|Minecraft}}'', but they do eventually start. Minecraft was previously referenced in [[861: Wisdom Teeth]].

The scientists find no link between jelly beans and acne (the probability that the result is by chance is more than 5% i.e. ''p'' > 0.05) but then Megan and Cueball ask them to see if only one colour of jelly beans is responsible. They test 20 different colors each at a significance level of 5%. If the probability that each trial gives a false positive result is 1 in 20, then by testing 20 different colors it is now likely that at least one jelly bean test will give a false positive. To be precise, the probability of having ''no'' false positive in 20 tests is 0.9520 = 35.85%. Probability of having ''no'' false positive in 21 tests (counting the test without color discrimination) is 0.9521 = 34.06%.

This leads to a big newspaper headline saying '''Green Jelly Beans Cause Acne''' where it is said that they have 95 percent confidence with only a 5% chance of a coincidence. Unfortunately, although this number has been reported by the scientists' stats package and would be true if green jelly beans were the only ones tested, it is also seriously misleading. If you roll just one die, one time, you aren't very likely to roll a six... but if you roll it 20 times you are very likely to have at least one six among them. This means that you cannot just ignore the other 19 experiments that failed.

There are good methods for handling this problem, notably {{w|Bayesian_inference|Bayesian inference}}, but they can be difficult to use and explain, and complexity does not sell newspapers.
In the title text we find out that the scientists {{w|Reproducibility|repeated the experiment}} (another key part of the scientific method), but now they no longer find any evidence for the link between acne and green jelly beans. They try to tell the reporter something, maybe that it was probably a coincidence, but the reporters are not interested since that is not news. So they do not listen to what the scientist has to say and instead uses the information they have to make another major headline saying '''Research conflicted''' and recommend more study on the link. But that was just what the scientist already did.

This is (sadly) often an issue with more serious matters than jelly beans and acne – at any one time there are many studies about possible links between substances (e.g. red wine) and illness (e.g. cancer). Because only the positive results get reported, this limits the value any single study has - especially if the mechanism linking the two things is not known.

=== p-hacking and bad news reporting in real life ===
In 2015 some journalists demonstrated the same problem: just how gullible other news outlets are with the same sort of flawed "experimental design": [http://www.washingtonpost.com/news/morning-mix/wp/2015/05/28/how-and-why-a-journalist-tricked-news-outlets-into-thinking-chocolate-makes-you-thin/?hpid=z5 How, and why, a journalist tricked news outlets into thinking chocolate makes you thin - The Washington Post]

==Transcript==
:[A girl with a black ponytail runs up to Cueball, who subsequently points off-panel where there are presumably scientists.]
:Girl with black ponytail: Jelly beans cause acne!
:Cueball: Scientists! Investigate!
:Scientist (off screen): But we're playing Minecraft!
:Scientist (off screen): ...Fine.

:[Two scientists. The man has safety goggles on, Megan has a sheet of notes.]
:Scientist with goggles: We found no link between jelly beans and acne (p > 0.05).

:[Back to the original two.]
:Cueball: That settles that.
:Girl with black ponytail: I hear it's only a certain color that causes it.
:Cueball: Scientists!
:Scientist (off screen): But Miiiinecraft!

:[20 identical small panels follow, 4 rows 5 columns. The exact same picture as in panel 2 above. The scientist with goggles are stating the results and Megan holds some notes in her hand. The only difference from panel to panel is the color and then in the 14th panel where the result is positive and there is an exclamation from off screen.]
:Scientist with goggles: We found no link between purple jelly beans and acne (p > 0.05).

:Scientist with goggles: We found no link between brown jelly beans and acne (p > 0.05).

:Scientist with goggles: We found no link between pink jelly beans and acne (p > 0.05).

:Scientist with goggles: We found no link between blue jelly beans and acne (p > 0.05).

:Scientist with goggles: We found no link between teal jelly beans and acne (p > 0.05).

:Scientist with goggles: We found no link between salmon jelly beans and acne (p > 0.05).

:Scientist with goggles: We found no link between red jelly beans and acne (p > 0.05).

:Scientist with goggles: We found no link between turquoise jelly beans and acne (p > 0.05).

:Scientist with goggles: We found no link between magenta jelly beans and acne (p > 0.05).

:Scientist with goggles: We found no link between yellow jelly beans and acne (p > 0.05).

:Scientist with goggles: We found no link between grey jelly beans and acne (p > 0.05).

:Scientist with goggles: We found no link between tan jelly beans and acne (p > 0.05).

:Scientist with goggles: We found no link between cyan jelly beans and acne (p > 0.05).

:Scientist with goggles: We found a link between green jelly beans and acne (p < 0.05).
:Voice (off screen): ''Whoa!''

:Scientist with goggles: We found no link between mauve jelly beans and acne (p > 0.05).

:Scientist with goggles: We found no link between beige jelly beans and acne (p > 0.05).

:Scientist with goggles: We found no link between lilac jelly beans and acne (p > 0.05).

:Scientist with goggles: We found no link between black jelly beans and acne (p > 0.05).

:Scientist with goggles: We found no link between peach jelly beans and acne (p > 0.05).

:Scientist with goggles: We found no link between orange jelly beans and acne (p > 0.05).

:[Newspaper front page with a picture with three green jelly beans. There are several sections with unreadable text below each of the last three readable sentences.]
:'''News'''
:'''Green Jelly Beans Linked To Acne!'''
:95% Confidence
:Only 5% chance of coincidence!
:Scientists...

{{comic discussion}}
[[Category:Comics with color‏‎]]
[[Category:Comics featuring Cueball]]
[[Category:Comics featuring Megan]]
[[Category:Statistics]]
[[Category:Video games]]
[[Category: Research Papers]]

2435: Geothmetic Meandian

2021-03-16T07:31:48Z

162.158.134.38: /* Explanation */

{{comic
| number = 2435
| date = March 10, 2021
| title = Geothmetic Meandian
| image = geothmetic_meandian.png
| titletext = Pythagorean means are nice and all, but throwing the median in the pot is really what turns this into random forest statistics: applying every function you can think of, and then gradually dropping the ones that make the result worse.
}}

==Explanation==

There are a number of different ways to identify the '{{w|average}}' value of a series of values, the most common unweighted methods being the {{w|median}} (take the central value from the ordered list of values if there are an odd number - or the value half-way between the two that straddle the divide between two halves if there are an even number) and the {{w|arithmetic mean}} (add all the numbers up, divide by the number of numbers). The {{w|geometric mean}} is less well-known but works similarly to the arithmetic mean. The geometric mean of 'n' positive numbers is the 'n'th root of the product of those numbers. If all of the numbers in a sequence are identical, then its arithmetic mean, geometric mean and median will be identical, since they would all be equal to the common value of the terms of the sequence. However, if the sequence is not constant, then {{w|Inequality_of_arithmetic_and_geometric_means#Geometric_interpretation|the arithmetic mean will be greater than the geometric mean}}, and the median may be different than either of those means.

The geometric mean, arithmetic mean and {{w|harmonic mean}} (not shown) are collectively known as the {{w|Pythagorean means}}, as specific modes of a greater and more generalized mean formula that extends arbitrarily to various other possible nuances of mean-value rationisations (cubic, etc.).

{{w|Outlier}}s and internal biases within the original sample can make boiling down a set of values into a single 'average' sometimes overly biased by flaws in the data, with your choice of which method to use perhaps resulting in a value that is misleading, exaggerating or suppressing the significance of any blips.



In this depiction, the three named methods of averaging are embedded within a single function that produces a sequence of three values - one output for each of the methods. Being a series of values, Randall suggests that this is ideally suited to being ''itself'' subjected to the comparative 'averaging' method. Not just once, but as many times as it takes to narrow down to a sequence of three values that are very close to one another.

It can be shown that the xkcd value of 2.089 for GMDN(1,1,2,3,5) is validated:

{|-
| F0 || 1 || 1 || 2 || 3 || 5
|-
| || Arithmetic mean || Geometric mean || Median ||
|-
| F1 || 2.4 || 1.974350486 || 2
|-
| F2 || 2.124783495 || 2.116192461 || 2
|-
| F3 || '''2.080325319''' || 2.079536819 || 2.116192461
|-
| F4 || 2.0920182 || 2.091948605 || '''2.080325319'''
|-
| F5 || '''2.088097374''' || 2.088090133 || 2.091948605
|-
| F6 || 2.089378704 || 2.089377914 || '''2.088097374'''
|-
| F7 || '''2.088951331''' || 2.088951244 || 2.089377914
|-
| F8 || 2.089093496 || 2.089093487 || '''2.088951331'''
|-
| F9 || '''2.089046105''' || 2.089046103 || 2.089093487
|-
| F10 || 2.089061898 || 2.089061898 || '''2.089046105'''
|}

The function GMDN in the comic is properly defined in the second row since F acts on a vector to produce another three vector, however GMDN in the last line is shown to produce a single real number rather than a vector and is thus missing a final operation of returning a single component. Each row in this table shows the set Fn(..) composed of the average, geomean and median computed on the previous row, with the sequence {1,1,2,3,5} as the initial F0. While GMDN is not differentiable, due to the median, this can be interpreted as somewhat similar to a heat equation which approaches equilibrium through averaging. Interestingly, the maximum value alternates between the average and the median (highlighted in bold in the table), while the minimum value alternates between the geomean and the median. This holds for many inputs thus providing the basis for a possible proof-by-induction of convergence on the range (see discussions).

The comment in the title text about suggests that this will save you the trouble of committing to the 'wrong' analysis as it gradually shaves down any 'outlier average' that is unduly affected by anomalies in the original inputs. It is a method without any danger of divergence of values, since all three averaging methods stay within the interval covering the input values (and two of them will stay strictly within that interval).

The title text may also be a sly reference to an actual mathematical theorem, namely that if one performs this procedure only using the arithmetic mean and the harmonic mean, the result will converge to the geometric mean. Randall suggests that the (non-Pythagorean) median, which does not have such good mathematical properties with relation to convergence, is, in fact, the secret sauce in his definition.

The question of being unsure of which mean to use is especially relevant for the arithmetic and harmonic means in following example.
* Cueball has some US Dollars and wishes to buy Euros. Suppose the bank will exchange US Dollars to Euros at a rate of €5 for $6 (about 0.83333€/$ or 1.20000$/€).
* Megan has some Euros and wishes to buy US Dollars. Suppose the bank will exchange Euros to US Dollars at a rate of $7 for €6 (about 0.85714€/$ or 1.16667$/€).
[[Cueball]] and [[Megan]] decide to complete the exchange between themselves in order to save the {{w|Bid-ask spread}} of the {{w|Exchange rate}} which is the cost the bank imposes on Cueball and Megan for its service as a {{w|Market maker}}.
* Cueball offers to split the difference by averaging the rates €5:$6 and €6:$7 yielding a rate of €71:$84 (about 0.84524€/$ or 1.18310$/€).
* Megan offers to split the difference by averaging the rates $6:€5 and $7:€6 yielding a rate of €60:$71 (about 0.84507€/$ or 1.18333$/€).
In one direction (€/$), Cueball is using the arithmetic mean but Megan is using the geometric mean while in the other direction ($/€), Megan is using the arithmetic mean but Megan is using the geometric mean. This creates two new exchange rates which are closer than the orginal rates, but the new rates are still different for each other. Megan and Cueball can then iterate this process and the rates will converge to the geometric mean of the original rates namely:
* sqrt((5/6)*(6/7)) = sqrt(5/7) = 0.84515€/$ or
* sqrt((6/5)*(7/6)) = sqrt(7/5) = 1.18322$/€.

There does exist an {{w|arithmetic-geometric mean}}, which is defined identically to this except with the arithmetic and geometric means, and sees some use in calculus. In some ways it's also philosophically similar to the {{w|truncated mean}} (extremities of the value range, e.g. the highest and lowest 10%s, are ignored as not acceptable and not counted) or {{w|Winsorized mean}} (instead of ignored, the values are readjusted to be the chosen floor/ceiling values that they lie beyond, to still effectively be counted as 'edge' conditions), only with a strange dilution-and-compromise method rather than one where quantities can be culled or neutered just for being unexpectedly different from most of the other data.

The input sequence of numbers (1,1,2,3,5) chosen by Randall is also the opening of the {{w|Fibonacci sequence}}. This may have been selected because the Fibonacci sequence also has a convergent property: the ratio of two adjacent numbers in the sequence approaches the [https://en.wikipedia.org/wiki/Golden_ratio#Relationship_to_Fibonacci_sequence golden ratio] as the length of the sequence approaches infinity.

Here is a table of averages classified by the various methods referenced

{|border =1 width=100% cellpadding=5 class="wikitable"
|+ averages using various methods
! Method
! Value
! Formula
|-
! Arithmetic
| 2.4 ||
|-
! Geometric
| 1.9743504858348
| <math>\left(\prod_{i=1}^n x_i\right)^\frac{1}{n} = \sqrt[n]{x_1 x_2 \cdots x_n}</math>
|-
! Median
| 2 ||
|-
! GMDN
| 2.089 ||
|}

==Transcript==
{{incomplete transcript|Do NOT delete this tag too soon.}}

F(x1,x2,...xn)=({x1+x2+...+xn/n [bracket: arithmetic mean]},{nx,x2...xn, [bracket: geometric mean]} {x n+1/2 [bracket: median]})

Gmdn(x1,x2,...xn)={F(F(F(...F(x1,x2,...xn)...)))[bracket: geothmetic meandian]}

Gmdn(1,1,2,3,5) [equals about sign] 2.089

Caption: Stats tip: If you aren't sure whether to use the mean, median, or geometric mean, just calculate all three, then repeat until it converges

==Trivia==
Geothm means "counting earths" (From Ancient Greek γεω- (geō-), combining form of γῆ (gê, “earth”) and ἀριθμός arithmos, 'counting'). Geothmetic means "art of Geothming" based on the etymology of Arithmetic (from Ancient Greek ἀριθμητική (τέχνη) (arithmētikḗ (tékhnē), “(art of) counting”). This is an exciting new terminology that is eminently suitable for modern cosmology & high energy physics - particularly when doing math on the multiverse. However, it is unlikely this etymology is related to the term "geothmetic meandian" as coined by Randall, as it can be more simply explained as a portmanteau of the three averages in its construction: '''geo'''metric mean, ari'''thmetic mean''', and me'''dian'''.

The following python code (inefficiently) implements the above algorithm:

<pre>
from functools import reduce

def f(*args):
args = sorted(args)
mean = sum(args) / len(args)
gmean = reduce(lambda x, y: x * y, args) ** (1 / len(args))
if len(args) % 2:
median = args[len(args) // 2]
else:
median = (args[len(args) // 2] + args[len(args) // 2 - 1]) / 2
return mean, gmean, median

max_iterations = 10
l = [1, 1, 2, 3, 5]
for iterations in range(max_iterations):
fst, *rest = l
if all((abs(r - fst) < 0.00000001 for r in rest)):
break
l = f(*l)
print(l[0], iterations)
</pre>
Here is a slightly more efficient version of the python code:

<pre>
from scipy.stats.mstats import gmean
import numpy as np

def get_centers(a,tol=0.00001):
a = np.array(a)
result = False
if len(a)==3:
if np.abs(a[0]-a[1])<=tol and np.abs(a[0]-a[2])<=tol and np.abs(a[2]-a[1])<=tol:
result=True
print([np.mean(a),np.median(a),gmean(a)])
if result:
return a[0]
return get_centers([np.mean(a),np.median(a),gmean(a)])

</pre>

And here is an implementation of the Gmdn function in R:

Gmdn <- function (..., threshold = 1E-6) {
# Function F(x) as defined in comic
f <- function (x) {
n <- length(x)
return(c(mean(x), prod(x)^(1/n), median(x)))
}
# Extract input vector from ... argument
x <- c(...)
# Iterate until the standard deviation of f(x) reaches a threshold
while (sd(x) > threshold) x <- f(x)
# Return the mean of the final triplet
return(mean(x))
}

{{comic discussion}}


[[Category:Math]]
[[Category:Statistics]]
[[Category:Portmanteau]]

Little Bobby Tables

2021-02-15T12:17:46Z

162.158.134.38: /* Appearances */ gender, not sex

{{Infobox character
| image = Little Bobby Tables.PNG
| imagesize =
| caption = First drawn drawing in [[342: 1337: Part 2]].
| first_appearance = [[327: Exploits of a Mom]]
}}

'''<code>Robert'); DROP TABLE students;--</code>''', nicknamed '''Little Bobby Tables''', is the youngest son of elite hacker [[Mrs. Roberts]]. His elder sister is [[Elaine Roberts|Help I'm trapped in a driver's license factory Elaine Roberts]]. His "full" name is known to cause problems with some computers. When he was first enrolled in school ([[327: Exploits of a Mom]]), it exploited a vulnerability in the parsing of students' names into the school's student database resulting in the school losing all the student records for the year.

In {{w|SQL}}, commands are terminated by semicolons '''<code>;</code>''' and data is often quoted using single quotes '''<code>'</code>'''. Commands may also be enclosed in parentheses '''<code>(</code>''' and '''<code>)</code>'''. Data is stored in tables of similar items (e.g. '''<code>students</code>''') and individual entries are "rows" in the table. To delete an entire table (and every row of data in that table), you use the command '''<code>DROP</code>''' (e.g. '''<code>DROP TABLE students</code>'''). The '''<code>--</code>''' represents the start of a {{w|Comment_(computer_programming)#SQL|SQL comment}} which ensures that the rest of the command is ignored so an error will not occur.

The exploited vulnerability is that the single quote in the name input was not properly "escaped" by the software. Thus, when the name is embedded into some SQL statement, the quote is erroneously parsed as a closing quote inside that statement, rather than being parsed as part of the name. Lack of such escaping is a common SQL vulnerability; this type of exploit is referred to as {{w|SQL injection}}.

The name Bobby Tables inspired a website, [http://bobby-tables.com/ bobby-tables.com], a guide for beginning programmers to learn the right way to avoid SQL injection in their code. A similarly named character, Mister Rogers, appears in [[884: Rogers St.]], with the same code injection in his middle name. It appears in [[1253: Exoplanet Names]] as one of the suggested planet names.

== Appearances ==
In the five comics he is referenced he is only drawn three times. The first two is in the [[:Category:1337|1337 series]] where he is drawn as a Cueball-like kid. See picture above. But then he also appears as a young man with long curly hair, looking very much like a woman in [[884: Rogers St.]] Here it is only the title text that reveals that this is Bobby, that and the fact that [[Randall]] in the official transcript does not mention the gender, but only that it is a person.

Here is how he looks in that comic: 
[[File:Adult Bobby Tables.PNG]]

There have been suggestions that the Robert in the table in [[596: Latitude]] was Bobby, but given that [[Black Hat]] has never had any relation to him in the other comics, and that [[Rob]] has, it seems more likely that the Robert is Rob.

== Example of SQL injection ==

A typical, unsecured SQL command vulnerable to SQL injection would be something like:

database.execute("INSERT INTO students (name) VALUES ('" + name + "');");

where <code>name</code> is a variable which is filled with the name to be inserted into the database. With a regular name, this would result in the following SQL command to be sent to the database system:

INSERT INTO students (name) VALUES ('Elaine');

However, with Little Bobby Tables's full name, the SQL command would be:

INSERT INTO students (name) VALUES ('Robert'); DROP TABLE students;--');

Or, if split after each <code>;</code>:

INSERT INTO students (name) VALUES ('Robert');
DROP TABLE students;
--');

The first commands inserts the name <code>Robert</code> into the database as in the first example. The second command however completely deletes the table <code>students</code>. The remainder is a comment to prevent syntax errors with the apostrophe and the closing parenthesis.

== Real Life occurrence ==

In French-speaking countries, apostrophes are a common character in street names. More often than not, French speakers unwittingly trigger SQL injection bugs when trying to order something from a US shop. In Italy, they are often part of town names, too (e.g. {{w|L'Aquila}}).

==See also==
*[[:Category:Comics featuring Little Bobby Tables|Comics featuring Little Bobby Tables]]

{{navbox-characters}}
[[Category:Characters]]