Editing 881: Probability

{{comic
| number    = 881
| date      = April 4, 2011
| title     = Probability
| image     = probability.png
| titletext = My normal approach is useless here, too.
}}

==Explanation==

[[Cueball]] and [[Megan]] are sitting on a hospital bed, reading a piece of paper with the statistics for {{w|breast cancer}} survival. It looks like Megan has just been diagnosed with breast cancer. The thick line represents the survival rate distribution (probability to be alive after X years, unconditioned): 81% are alive at 5 years, while 77% survive to 10 years. The dashed line represents the {{w|hazard function}} (the negative derivative of the thick line divided by the value of the thick line at each point, i.e. how fast the thick line falls with respect to the current value, or the risk of failing/dying at time t+Δt after having survived until time t as Δt approaches zero), which is the rate between the density of the failure distribution and the survival function. Cueball expresses how he used to find probability enjoyable because of its applicability to the real world, but now sees things differently facing a painful situation involving it.

[[Randall]] wrote this comic after his fiancee was diagnosed with breast cancer. Two months after posting this strip, he posted [http://blog.xkcd.com/2011/06/30/family-illness/ this blog post] explaining the [[:Category:Cancer|cancer comics]].

The title text is a reference to [[55: Useless]], where his normal approach also fails him regarding love. Cueball's (and Randall's) normal approach — math — isn't much help in dealing with ''these''  types of emotional situations.

A number of further comics have addressed this scenario, in particular the retrospective and occasional series of comics [[1141: Two Years]], [[1928: Seven Years]] and [[2386: Ten Years]].


==Transcript==
:[A plot of percent vs. years, with a solid and a dashed line. The solid line starts at 100%, and drops constantly. The dashed line starts around 85%, rises to 95% after 5 years, then drops.]

:[A simple table.]
:;5 years
::81%
:;10 years
::77%

:[Cueball and Megan are sitting on a bench, next to an Intravenous drip hanging from a rack. Cueball is holding a paper.]
:Cueball: You know, probability used to be my favorite branch of math
:Cueball: Because it had so many real-life applications.

:[They embrace, faces together.]

{{comic discussion}}
[[Category:Comics featuring Cueball]]
[[Category:Comics featuring Megan]]
[[Category:Romance]]
[[Category:Cancer]]
[[Category:Charts]]
[[Category:Line graphs]]
[[Category:Math]]
[[Category:Statistics]]