https://www.explainxkcd.com/wiki/api.php?action=feedcontributions&user=162.158.158.237&feedformat=atomexplain xkcd - User contributions [en]2024-03-19T06:03:59ZUser contributionsMediaWiki 1.30.0https://www.explainxkcd.com/wiki/index.php?title=2308:_Mount_St._Helens&diff=1925462308: Mount St. Helens2020-05-27T10:18:58Z<p>162.158.158.237: /* Explanation */</p>
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<div>{{comic<br />
| number = 2308<br />
| date = May 18, 2020<br />
| title = Mount St. Helens<br />
| image = mount_st_helens.png<br />
| titletext = It's a good mountain but it really peaked in the 80s.<br />
}}<br />
<br />
==Explanation==<br />
This comic marks the 40 year anniversary of the {{w|1980 eruption of Mount St. Helens|May 18, 1980 eruption of Mount St. Helens}} that killed 57 people. It was a Monday so a normal release day could be used to mark this event.<br />
<br />
It shows a graph of the height of the mountains in the {{w|Washington (state)|state of Washington}} as a function of time over the last 100 years. The only mountain to change its height significantly over this time period is {{w|Mount St. Helens}}, which the comic is named after. It is also the only black line as all other (30?) lines are gray.<br />
<br />
Mount St. Helens is a {{w|volcano}} that famously and explosively erupted in 1980. Millions of tons of earth were blasted from one face of the mountain all over the surrounding countryside. After it was over, the peak of Mount St. Helens was no longer the 5th highest in the {{w|Washington (state)|state of Washington}}, having lost approximately 1,300 feet (400 m) in height (from 9,677 ft (2,950 m) pre-explosion to 8,363 ft (2,549 m) post-explosion). <br />
<br />
The comic shows an rare event that had major effect and was predictable in hindsight, but would have surprised an observer that is just tracking the height of Mt. St. Helens in a non-representative timeframe. Such an event is called a {{w|Michele_Wucker|Gray Rhino}} event. <br />
Interesting the horizontal axis shows an observation data period between 1920 and 2020. During this observation period both the 1918 {{w|Spanish flu}} and 2020 {{w|COVID-19 pandemic}} (each also Gray Rhino events) could have been overlooked in a similar way.<br />
<br />
Currently, the 5 highest {{w|List of mountain peaks of Washington (state)|mountain peaks in Washington State}} are {{w|Mount Rainier}} (at 14,411 ft or 4,392 m), {{w|Mount Adams (Washington)|Mount Adams}}, {{w|Mount Baker}}, {{w|Glacier Peak}}, and {{w|Bonanza Peak (Washington)|Bonanza Peak}}. As shown in the comic, Mount St. Helens was the 5th highest, but now has fallen to #35 (using a {{w|topographic prominence}} cut-off of 500 m (1640 feet)). Only mountains above 8,000 feet (2,438 m) are included, with the graph topping at 15,000 feet (4,572 m), 600 feet (182 m) above the highest mountain. There are 92 peaks above 8000 feet in the state, so not all are included and the lines are not really distinct below 9000 feet. Seems like there are less than 30 lines drawn. Of course it says Mountains not Mountain peaks, but there are only four mountain ranges in Washington with peaks above 8000, so he must mean peaks!<br />
<br />
Technically, the other mountains may be fluctuating in height as well, due to erosion or the movement of Earth's tectonic plates, but this phenomenon should not be visible on the time-scale and vertical resolution that Randall has plotted. <!-- Or are they rising on average due to the Cascadia Subduction Zone?--> Precision GPS measurements of various peaks in Washington have only been available since 2010, and it's likely that the primarily volcanic mountains of Washington experience significant but comparatively slight variations throughout the year due to snowfall, melt, or the pressure of swelling magma inside volcanic cores. These changes go largely unmeasured, while the mountains continue to appear equally physically unchanging and imposing both in person and from a distance.<br />
Source: [https://www.seattletimes.com/seattle-news/how-tall-is-rainier-really/ Seattle Times]. So while the comic does appear to show some slight fluctuations in height for mountains, that is more likely a side-effect of the comic's free-hand drawing style than an accurate reflection of any real fluctuations.<br />
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The title text is a play on the term "peak" meaning both the highest point of a mountain and also the optimal, most famous or most impressive stage of a trend; for instance: "The band Rolling Stones really peaked in the 80s."<br />
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==Transcript==<br />
:[Caption above graph:]<br />
:Heights of mountains in Washington State<br />
:<small>Over time</small><br />
<br />
:[A graph is shown with close to 30 horizontal gray lines which seem not to change much, if any, as they go from left to right. Only the top 6 gray lines are distinctly separated from others. The top line is way above the second line which again is far above the next two that are close together. Two more close together is somewhat further down, and just below them the rest of the lines follow in close proximity down to the bottom of the graph. A single black line is also shown. It begins as the fifth highest line, just above the two last mentioned above. It, like all other lines, goes horizontally, but only three fifths of the way across the graph – then it immediately drops down well below most of the other lines (at 1980) and levels off, continuing on its horizontal path. There is a caption above the graph, and both Y-axis and X-axis has labels. For the Y-axis there is a tick for every label, for the X-axis only every 2nd tick has a label. A unit is given on the top label on the Y-axis.]<br />
<br />
:[X-axis:]<br />
:1920 1940 1960 1980 2000 2020<br />
<br />
:[Y-axis:]<br />
:15,000<br />
::<small>feet</small><br />
:14,000<br />
:13,000<br />
:12,000<br />
:11,000<br />
:10,000<br />
:9,000<br />
:8,000<br />
<br />
{{comic discussion}}<br />
<br />
[[Category:Line graphs]]<br />
[[Category:Timelines]]<br />
[[Category:Geology]]<br />
[[Category:Volcanoes]]</div>162.158.158.237https://www.explainxkcd.com/wiki/index.php?title=2303:_Error_Types&diff=1925452303: Error Types2020-05-27T10:17:58Z<p>162.158.158.237: /* Explanation */</p>
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<div>{{comic<br />
| number = 2303<br />
| date = May 6, 2020<br />
| title = Error Types<br />
| image = error_types.png<br />
| titletext = Type IIII error: Mistaking tally marks for Roman numerals<br />
}}<br />
<br />
==Explanation==<br />
This comic is another comic in a [[:Category:COVID-19|series of comics]] related to the {{w|2019–20 coronavirus outbreak|2020 pandemic}} of the {{w|coronavirus}} {{w|SARS-CoV-2}}, which causes {{w|COVID-19}}. <br />
<br />
The comic is inspired by the COVID-19 pandemic, as there is a lot of medical testing for the disease being done, including detection of the virus itself, usually by qPCR, or of antibodies present in people who have had the disease (sometimes unknowingly). The quality of these tests is often mediocre and never perfect, leading to discussion of different types of errors that can occur, including "false positives" (calling presence of the virus/antibodies when they are not really there) or false negatives (failing to see the virus/antibodies which are present). <br />
The comic is riffing on {{w|Type I and type II errors}}, also known as "false positive" and "false negative", respectively. The first two rows of the comic's table are correct definitions for established terms in statistics. Further rows contain suggestions for new terminology. <br />
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<br />
{|class = "wikitable"<br />
|+Explanation of error types<br />
|-<br />
!Type<br />
!Description<br />
!Explanation<br />
|-<br />
|Type I<br />
|{{w|False_positives_and_false_negatives#False_positive_error|False positive}}<br />
|A false positive is a result that indicates a correlation, when there is no correlation in reality. For example, a person may test positive (indicating that they have a disease), but in actuality they ''do not'' have the disease. Most diseases are only present in a small fraction of a population, so a test for that disease will usually produce more false positives than false negatives; this is why tests are usually not administered universally but only to patients with other diagnostic criteria, and sometimes multiple tests are used for additional certainty before embarking on serious, invasive treatments.<br />
|-<br />
|Type II<br />
|{{w|False_positives_and_false_negatives#False_negative_error|False negative}}<br />
|A false negative is a result that indicates no correlation, when there is a correlation in reality. For example, a person may test negative (indicating that they do not have a disease), but in actuality they ''do'' have the disease. Several previous XKCD comics have been about trivial "tests" for rare conditions that always return a negative result (e.g. [[2236: Is it Christmas?]] and [[937: TornadoGuard]]). Because most days it is not Christmas, and most people are not near a tornado, the "test" is technically correct a high percentage of the time, but for those circumstances when the condition is true, a false negative may be extremely costly.<br />
|-<br />
|Type III<br />
|True positive for incorrect reasons<br />
|"{{w|Type III error}}" is a nonstandard term meant to build off the notion of type I and II errors. Randall's explanations of this and of Type IV errors line up with some relatively common definitions of them, but others have also been proposed. None have yet been widely adopted. The Type III and Type IV definitions given here correspond to the {{w|Gettier_problem|Gettier Problem}} in philosophy. In the case of COVID-19, this type of error might be committed by a person who correctly believes himself to have COVID-19 but incorrectly believes so on the basis of living near a 5G tower.<br />
|-<br />
|Type IV<br />
|True negative for incorrect reasons<br />
|Randall's proposed Type III and Type IV errors refer to when a correct correlation or lack thereof is determined, but on faulty grounds. Although harmless in the present, this may lead to false faith in the results at a later date, as the faulty grounds of the result may lead to a type I or type II error in different circumstances. In the case of COVID-19, this type of error might be committed by a person who correctly believes himself to not have COVID-19 but incorrectly attributes this result to wearing a tinfoil hat.<br />
|-<br />
|Type V<br />
|Incorrect result which leads you to a correct conclusion due to unrelated errors<br />
|Here we get into errors entirely made up by Randall. The idea behind this one is that a botched statistical test might accidentally result in a true conclusion due to completely unrelated errors in the other direction--perhaps during data collection or aggregation. This could be the type of error experienced by a person whose test result is a false positive or negative, but which is then mis-typed into the electronic medical record, so that the correct result is returned to the doctor and patient after all.<br />
|-<br />
|Type VI<br />
|Correct result which you interpret wrong<br />
|An unfortunately common occurrence. For example, statistical tests on observational data can only determine correlation, not causation, yet press releases and subsequent popular articles often imply or explicitly state a causal relationship ([[882: Significant|"Jelly beans cause acne!"]] or whatnot). This has actually been [https://en.wikipedia.org/wiki/Type_III_error#Marascuilo_and_Levin proposed as a definition of a Type IV error]. Coincidentally, "Type VI" could be misread as "Type IV", making an incorrect reading be interpreted as the older definition of Type IV. Some kinds of coronavirus antibody tests have been found to return positive if the patient has ever had an infection by ''any'' coronavirus (e.g. some common colds), not just SARS-CoV-2, so the patient could test positive but incorrectly attribute that result to COVID-19.<br />
|-<br />
|Type VII<br />
|Incorrect result which produces a cool graph<br />
|It is commonly believed that [https://www.reddit.com/r/dataisbeautiful/ data is beautiful]. Sometimes, that's still true even when the data is bogus! A few days after this comic was released (May 9th), the Georgia Department of Public Health published a graph [http://www.joeydevilla.com/2020/05/17/georgia-department-of-healths-master-class-on-misinforming-with-statistics/ purporting to show a decline] in cases of COVID-19 over the previous two weeks, but which had actually been arranged so that the days were ordered by decreasing cases, rather than by time.<br />
|-<br />
|Type VIII<br />
|Incorrect result which sparks further research and the development of new tools which reveal the flaw in the original results while producing novel correct results<br />
|A hypothetical example might be if the Fleischmann–Pons {{w|cold fusion}} experiment, discredited as it was, had by its investigation successfully prompted the discovery of a truly usable alternate technique. (So far, in reality, it seems not to have.)<br />
|-<br />
|Type IX<br />
|The Rise of Skywalker<br />
|''{{w|Star Wars: The Rise of Skywalker}}'' is the ninth and final film in the ''Star Wars'' Skywalker saga. It received far less critical acclaim than the previous two films in the sequel trilogy. The poor reviews suggest that the movie as a whole could be considered an error. Closing with an "error" that refers to Star Wars and has no discussion of statistics also serves as a non sequitur punchline.<br />
|-<br />
|Type IIII<br />
|Mistaking tally marks for Roman numerals<br />
|Title text. "I", "II", and "III" could be representations of the numbers one, two, and three in either {{w|tally marks}} or {{w|Roman numerals}}. It's only when you get to "IV" or "IIII" that it becomes apparent which system is being used. Some clocks use Roman numerals but with "IIII" instead of "IV" at the four o'clock position; the exact reason for this is unknown, but [https://www.electrictime.com/news/roman-iiii-vs-iv-on-clock-dials/ several plausible hypotheses] have been advanced. <br />
Coincidentally, Randall seemed to have initially made a typographical error of his own in this title text spelling the word "numerals" as "neumerals". The error has since been corrected.<br />
|}<br />
<br />
==Transcript==<br />
:[A list with nine entries. The left side has 9 types of errors numbered with Roman numerals. The right side has a description of each type of error:]<br />
:Type I Error: False positive<br />
:Type II Error: False negative<br />
:Type III Error: True positive for incorrect reasons<br />
:Type IV Error: True negative for incorrect reasons<br />
:Type V Error: Incorrect result which leads you to a correct conclusion due to unrelated errors<br />
:Type VI Error: Correct result which you interpret wrong<br />
:Type VII Error: Incorrect result which produces a cool graph<br />
:Type VIII Error: Incorrect result which sparks further research and the development of new tools which reveal the flaw in the original results while producing novel correct results<br />
:Type IX Error: The Rise of Skywalker<br />
<br />
==Trivia==<br />
*Randall seems to have, ironically, made a typographical error of his own when spelling the word "numerals" in the title text.<br />
**This was corrected later, but initially, the title text was: "Type IIII error: Mistaking tally marks for Roman '''neumerals'''."<br />
**This may be intentionally mispronouncing, because of [[https://www.explainxkcd.com/wiki/index.php/148:_Mispronouncing his hobby]].<br />
<br />
{{comic discussion}}<br />
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[[Category:Statistics]]<br />
[[Category:Star Wars]]</div>162.158.158.237https://www.explainxkcd.com/wiki/index.php?title=Talk:2311:_Confidence_Interval&diff=192514Talk:2311: Confidence Interval2020-05-26T10:56:04Z<p>162.158.158.237: </p>
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<div><!--Please sign your posts with ~~~~ and don't delete this text. New comments should be added at the bottom.--><br />
What's a millisigma?<br />
[[Special:Contributions/162.158.107.209|162.158.107.209]] 03:31, 26 May 2020 (UTC)Ven<br />
:Not an official scientific term - most likely referring to standard deviation. One standard deviation, or sigma, is the 68.3 % of values lying around the mean in a normal distribution. A millisigma in a standard deviation would be .0683 % of a normal distribution so that much variation would be bad? Not sure. [[Special:Contributions/172.69.63.203|172.69.63.203]] 05:23, 26 May 2020 (UTC)<br />
:: Actually, if you [https://www.wolframalpha.com/input/?i=integrate+1%2Fsqrt%282+*+pi%29+*+exp%28-x%5E2+%2F+2%29+from++-0.001+to+0.001 integrate] a normal distribution <math>\mathcal{N}(0,1)</math> from <math>-\frac{\sigma}{1000}=-0.001</math> to <math>+\frac{\sigma}{1000}=0.001</math>, you'll get a range of about 0.08% of all values. This would be bad because it would mean that, as big as the confidence interval appears in the picture, the more meaningful 1- or 3-sigma interval (whose size represents the uncertainty of the model) would be larger by a factor of 1250 or 3750, respectively. --[[User:Koveras|Koveras]] ([[User talk:Koveras|talk]]) 08:38, 26 May 2020 (UTC)<br />
:Perhaps you heard about [https://en.wikipedia.org/wiki/Six_Sigma Six Sigma], a quality method used by General Electric (among others) to keep specifications and processes within tiny tolerances. The six sigmas mean that even absolute (so-called) outliers in your production are within the strict tolerances. With milli-sigmas it is extremely seldom to get an acceptable result at all. Sebastian --[[Special:Contributions/108.162.229.234|108.162.229.234]] 10:53, 26 May 2020 (UTC)<br />
Can it be related to Covid19 pandemia and all those graphs that try to predict if it is in decline or not? [[User:Tkopec|Tkopec]] ([[User talk:Tkopec|talk]]) 08:27, 26 May 2020 (UTC)<br />
: No. But maybe it's related to the recent Mt. St. Helens comic... :p Seriously, not everything has to be related to the hot-button topic of the day.<br />
::''Au contraire, mes amis'', it is obvious to me that [[1: Barrel - Part 1]] is about socially isolating away from the [[8: Red Spiders|virus]]. (Remember to sign?) [[Special:Contributions/162.158.158.237|162.158.158.237]] 10:56, 26 May 2020 (UTC)</div>162.158.158.237