2696: Precision vs Accuracy

2022-11-10T04:45:32Z

Utterlybasil:

{{comic
| number = 2696
| date = November 9, 2022
| title = Precision vs Accuracy
| image = precision_vs_accuracy_2x.png
| imagesize = 501x462px
| noexpand = true
| titletext = 'Barack Obama is much less likely than the average cat to jump in and out of cardboard boxes for fun' is low precision, but I'm not sure about the accuracy.
}}

==Explanation==
{{incomplete|Created by BARACK OBAMA IN A CARDBOARD BOX. Further detail, sortable table? - Please change this comment when editing this page. Do NOT delete this tag too soon.}}
This comic parodies the difference between 'accuracy' and 'precision' with a table. {{w|Accuracy and precision}} are common concepts to be encountered in the scientific field and often students have issues with the differences between them. Accuracy concerns whether a statement is true, while precision concerns how detailed it is; it is possible for a statement to be one but not the other. The comic explores this concept by comparing {{w|Barack Obama}}, former President of the United States, with {{w|cat}}s. Confusingly, he measures different statistics of both Barack Obama and cats (sometimes measuring them in terms of cats) leaving the unwary reader just as confused as before.

Being precise is typical of calculations that roll out an excess of significant digits, often in the form of trailing decimals. Precision is lowered by using more rounded figures, or merely being comparative, but largely unaffected by whether the original values used were accurate or even correct. Accuracy is a cumulative function of the accuracy given to the intermediate values used for any calculation, and can be degraded by using figures that are themselves in some way inaccurate or imprecise. One part of confusion between the two is because being too precise usually decreases accuracy.

The numbers mentioned in the top row (high precision) of the table all use exactly the same digits, dictating that a full five digits of ''precision'' are used in them all. The most "valid" or correct value is a number that's very accurate and precise (see table). For the medium accuracy the number is an anagram of the 1st entry, giving a value that is reasonable but would be overly exact, whilst the low accuracy number is just a repeat of the first entry's digits with a shifted decimal but clearly at the wrong scale. For the latter, he replaces the thousands separator with the decimal point, perhaps as a visual pun.

The title text compares Obama's and cats' enjoyment of playing with cardboard boxes. While cats are known to do this,{{citation needed}} we don't know whether Obama does.

The day prior to the publication of this comic (November 8, 2022) was election day in the United States, so Randall may have been remembering Barack Obama's presidency at this time.

{| class="wikitable"
!Precision
!Accuracy
!Statement
!Explanation
|-
|High
|High
|Barack Obama was president for 70,128 hours
|This is the official length in hours of {{w|Barack Obama}}'s 8-year presidency, including 2 {{w|leap year|leap days}}. Obama served from January 20, 2009 through January 20, 2017, and his term officially began and ended at noon on those days. (There were three {{w|leap second|leap seconds}} during his presidency, though.)
|-
|High
|Medium
|Barack Obama weighs as much as 17.082 cats
|The accuracy would depend on the mass of the cats in question. Also a human's mass can vary by a few pounds in a small amount of time as meals are consumed, resources are used in metabolism and wastes are eliminated, and thus this may be overly precise due the margin of error in both the mass of cats and the mass of Mr. Obama. In 2016, Obama was [https://www.cnn.com/2016/03/08/politics/obama-medical-exam-loses-weight officially reported] to weigh 175 lb (79.3787 kg). [https://www.google.com/search?q=how+heavy+is+an+average+cat Google claims that an average cat weighs between 8.8 and 11 lbs], so this statement may be close to accurate.
|-
|High
|Low
|Barack Obama is 70.128 feet tall
|A highly precise (5 significant digits) measurement, but far from his actual height, published as 6'1".
The given value is more than an order of magnitude different from both him and {{w|Robert Wadlow|almost}} any other known human, whilst one of 7.0128 would ''only'' be about 15% off – still a low accuracy, but not outside the realms of possibility for an otherwise unknown person.
Coincidentally, Barack Obama is approximately 70 ''cat'' feet tall, using the paw size of a house cat to measure his height. Given the number of cat-related facts in the rest of the chart, this could be seen as rather appropriate.
|-
|Medium
|High
|Most cats have 4 legs
|Like many mammals, cats are quadrupeds, which means "four feet". Unless there is a genetic or other developmental issue, or an an injury that causes the loss of a limb, then cats generally have 4 legs.
|-
|Medium
|Medium
|Barack Obama is 6'1"
|While only as precise as the nearest inch, a common degree of rounding in that scale of measurement, that is the former president's published height.
[https://www.cnn.com/2016/03/08/politics/obama-medical-exam-loses-weight In 2016], Obama was said to have "grown" 0.5 inches in height, so there is a definite lack of consistency of exactly how tall he is. The examinations may have been made at different times of their respective days, with some spinal compression occurring all the time not laid in bed, and his current height is also not publically recorded; several years of gradual aging could also reduce his posture slightly, or sustaining his fitness (since experiencing the travails of office) may counteract this to a greater or lesser effect.
|-
|Medium
|Low
|Barack Obama has 4 legs
|Barack Obama, being a mammal, does qualify as a tetra-pod, but as a primate, his two forelimbs have been modified into arms and hands, and like other humans, he does not generally use them for locomotion, but to manipulate his environment, thus this is highly ''in''accurate.

|-
|Low
|High
|Most cats have legs
|A true (high accuracy) statement without much information (low precision).
|-
|Low
|Medium
|Barack Obama has fewer legs than your cat
|Again, this will depend on the cat (not to mention whether or not you actually have a cat), but in general, true.
|-
|Low
|Low
|Barack Obama's cat has hundreds of legs
|This statement has low accuracy, as Barack Obama owns a four-legged dog named Sunny, but is not known to have owned a cat, much less one with more legs than normal. It also has low precision, as "hundreds" could reasonably range from 200 to 900.
|-
|Low
|Unsure
|Barack Obama is much less likely than the average cat to jump in and out of cardboard boxes for fun
|Barack Obama has never publicly jumped in and out of cardboard boxes for fun,{{citation needed}} but the possibility that he does in private exists.
|}

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

:[A table with 3 rows and 3 columns]

{| class="wikitable"
|-
! !! High accuracy !! Medium accuracy !! Low accuracy
|-
! High precision
|Barack Obama was president for 70,128 hours||Barack Obama weighs as much as 17.082 cats||Barack Obama is 70.128 feet tall
|-
! Medium precision
|Most cats have 4 legs||Barack Obama is 6'1"||Barack Obama has 4 legs
|-
! Low precision
|Most cats have legs||Barack Obama has fewer legs than your cat||Barack Obama's cat has hundreds of legs
|}

{{comic discussion}}
[[Category:Statistics]]
[[Category:Comics featuring real people]]
[[Category:Cats]]

2622: Angular Diameter Turnaround

2022-05-23T15:41:42Z

Utterlybasil: /* Explanation */ Linked "the original iPhone" to the original iPhone

{{comic
| number = 2622
| date = May 20, 2022
| title = Angular Diameter Turnaround
| image = angular_diameter_turnaround.png
| titletext = Thank you to Katie Mack for teaching me about this effect, and to Janelle Shane for describing redshifts as 'like galaxies sinking into a pool of dilute blood,' which is how I'll see them from now on.
}}

==Explanation==
{{incomplete|Created by a Galaxy-branded phone with minimal writing experience- Please change this comment when editing this page. Do NOT delete this tag too soon.}}
This comic references multiple physics and maths concepts, including {{w|Angular diameter}}, {{w|Angular diameter distance}}, {{w|Redshift}}, and {{w|phones|mobile phones}}, although mobile phones are not a core science at this time.{{Citation needed}}

The comic shows the galaxies of the universe as Samsung Galaxy mobile phones, pairing the age we see them at from earth, the degree they are redshifted, and how much of the sky they take up, known as their angular diameter. The mobile phones that are closer and older have depleted batteries, whereas the batteries are full for those phones from which the light is still only beginning to reach us. This is how galaxies appear in the sky if they were phones that had batteries lasting billions of years, the light reaching us from deeper into the past as it comes from objects that are farther away. Phones at a low battery may be a reference to [[1373: Screenshot]], where Randall commented that it is hard to pay attention to any phone with a low battery as the need to charge it is so urgent.

An important takeaway from this comic is that the events that occurred at the very start of our universe are etched in our sky ''as if they are still happening now'', in a detailed faint timeline, that we are still learning more and more from. Using the mobile phone metaphor helps as, when the technology space was young and smaller there were {{w|mobile phones}}, such as {{w|iPhone (1st generation)|the original iPhone}}, which one might still remember despite there being many more recent and better ones in a more crowded market space.

Randall's intent appears to be to highlight how just a few very distant galaxies occupy incredibly large proportions of the sky and are seen as they were at a very young age. Mobile phones have this similarity, of massive presence, relatively early stages of new technology, and bringing information from far away.

The large galaxies can be seen in dark red in the background as if the unimaginably ancient child galactic bodies are looming forebodingly behind everything else. The title text refers to galaxies falling into a pool of dilute blood as if the void beyond were hell. This completely misses the point as to what redshift is, being an effect on the wavelength of light, rather than light being filtered through regions of infernal suffering or far galaxies being stained by the blood of the enemies of Android phones.

This physical concept has a lot of juxtaposition of things that usually contradict, and Randall has put energy into attempting to highlight that.

Katie Mack tweet: https://twitter.com/AstroKatie/status/1516548836709343238

{{w|Spacetime diagram}} possibly has reasonable visualizations of the kinds of relations bodies have when they are moving this far apart, including angular diameter distance. Simultaneity no longer exists at such distances. Distance is debated too, although that would be a different article.

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

:Angular Diameter Turnaround
:Illustrated using phones instead of galaxies
:(Brightness and redshift adjusted to keep phones visible)
:Things that are far away look smaller, but things that are ''really'' far away look ''bigger'', because when their light was emitted, the universe was small and they were close to us.

{{comic discussion}}
[[Category:Astronomy]]
[[Category:Math]]
[[Category:Physics]]
[[Category:Smartphones]]
[[Category:Comics with color]]
[[Category:Comics featuring real people]] 
[[Category:Puns]]

explain xkcd - User contributions [en]

2696: Precision vs Accuracy

2622: Angular Diameter Turnaround