Visual & Statistical Thinking

What Hacker News says

1. seliopouDec 2016
   Tufte wrote an essay on how the data available suggested that there was a high likelihood of O-ring failure, but that the data and findings were poorly communicated. This led to the decision to launch, the subsequent failure of the O-rings and loss of life. This essay appears in the booklet "Visual and Statistical Thinking"[0], among other publications, along with an other essay on how the source of cholera was traced to contaminated drinking water in 19th century London by John Snow. He plotted cholera cases on a map, and looked at where the outbreaks were most frequent.[1] This also led to the discovery of the vector of cholera, which up until then was unknown or at least misattributed. Both are great reads.

   [0]: https://www.sfu.ca/cmns/courses/2012/801/1-Readings/Tufte%20...

   [1]: https://en.wikipedia.org/wiki/1854_Broad_Street_cholera_outb...

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2. keithwinsteinDec 2016
   The Challenger explosion is a great case study. But in focusing on that chart from the Rogers Commission report, this piece reinforces what is basically a well-told fable about the Challenger disaster.

   The piece says: "Below is the key graph of the O-ring test data that NASA analyzed before launch" and reproduces the famous chart. It continues, "NASA management used the data behind this first graph (among many other pieces of information) to justify their view the night before launch that there was no temperature effect on O-ring performance [...] But NASA management made one catastrophic mistake: this was not that chart they should have been looking at."

   I think these statements are pretty misleading without some major caveats.

   Tufte ("Visual and Statistical Thinking: Displays of Evidence for Making Decisions"; https://blogs.stockton.edu/hist4690/files/2012/06/Edward-Tuf...) writes:

   "Most accounts of the Challenger reproduce a scatterplot that apparently demonstrates the analytical failure of the pre-launch debate. The graph depicts only launches with O-ring damage and their temperatures, omitting all damage-free launches (an absence of data points on the line of zero incidents of damage). First published in the shuttle commission report (PCSSCA, volume 1, 146), the chart is a favorite of statistics teachers. [...] The graph of the missing data-points is a vivid and poignant object lesson in how not to look at data when making an important decision. But it is too good to be true! First, the graph was not part of the pre-launch debate; it was not among the 13 charts used by Thiokol and NASA in deciding to launch. Rather, it was drawn after the accident by two staff members (the executive director and a lawyer) at the commission as their simulation of the poor reasoning in the pre-launch debate. Second, the graph implies that the pre-launch analysis examined 7 launches at 7 temperatures with 7 damage measurements. That is not true; only 2 cases of blow-by and 2 temperatures were linked up. The actual pre-launch analysis was much thinner than indicated by the commission scatterplot. Third, the damage scale is dequantified, only counting the number of incidents rather than measuring their severity. In short, whether for teaching statistics or for seeking to understand the practice of data graphics, why use an inaccurately simulated post-launch chart when we have the genuine 13 pre-launch decision charts right in hand?"

   (For a response to Tufte's essay, see https://people.rit.edu/wlrgsh/FINRobison.pdf, also cited elsewhere here.)

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3. danekFeb 2016
   I was wrong--he wasn't going be attend, but there (allegedly) were plans to have a televised conversation between him and Christa McAuliffe during his State of the Union address that night.

   However this may not be true. While trying to find an e-source, I read that there were some politically-motivated rumors that the white house ordered the shuttle to launch for this reason. Feynman investigated that rumor and didn't find any evidence that the white house ordered the launch.

   It's possible the detail about an on-air tv conversation between the president and a schoolteacher astronaut could have been fabricated as well to make Reagan look bad, or it could have been based on elements of truth. For example she was expected to broadcast 2 lessons to students from space, so the capability definitely existed. It doesn't seem too far out that they would have liked for this conversation to happen during the State of the Union, though that doesn't mean the white house ordered the launch.

   I read this in Edward Tufte's essay Visual and Statistical Thinking (http://www.edwardtufte.com/tufte/books_textb), which discusses how better information displays might have convinced NASA management to postpone the launch. It also appears as a chapter in his book Visual Explanations.

   I didn't have any luck finding sources on the internet (lots of keyword overlap). Tufte is much better informed than pretty much all of us, though it's possible he printed what amounts to an unsubstantiated rumor. FWIW he also served on the Columbia accident investigation board.

   I think there were other pressures to launch as well. The launch date had been postponed 3 times already for various reasons. Cynical danek: I wouldn't be too surprised if some manager's performance review was based on how many launches took place on the scheduled date.

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