Tufte criticizes Boeing report on Columbia foam impact

Subject: Tufte criticizes Boeing report on Columbia foam impact
From: Keith Soltys <keith -at- soltys -dot- ca>
To: "TECHWR-L" <techwr-l -at- lists -dot- raycomm -dot- com>
Date: Fri, 21 Mar 2003 06:54:10 -0500


In light of the recent discussions of Edward Tufte's criticisms of the way bad data presentation contributed to the Challenger disaster, I thought that this might be relevant:

http://www.edwardtufte.com/714883858/bboard/q-and-a-fetch-msg?usca_p=t&msg_id=0000Rs&topic_id=1

On this page he critiques the slides used by Boeing to assess the damage caused to Columbia by the foam strike.

Much of the criticism is in the form of jpeg images, but here's a plain text excerpt from the page:

"The 3 reports have the following weaknesses: It now appears that the conclusions were incorrect. The results appear sensitive to input assumptions about incidence angle, incidence location, the number and velocity of impacts, and the weight of the debris (assumed to be lightweight foam at 2.4 pounds/cubic foot)--and that multivariate sensitivity is not carefully examined. In the video of the debris impact, the debris pieces look larger than the estimated sizes (20" by 10" by 6"; and 20" by 16" by 6") used in the 3 reports. The important video is at http://www.spaceref.com/Columbia/post.launch.video.html The video also shows a fine shower of debris coming off the wing after impact; that spray does not immediately suggest foam chips. In the reports, assumptions tend to be evaluated generally in the direction of how they might reduce the seriousness of the threat (after-the fact arguments of the form "this is a conservative estimate" replace careful quantitative estimates of robustness and uncertainty). An important table has 2 empty cells; threat assessments are missing in those 2 cells. The good diagram showing forecasted tile loss provides only point estimates; there is no cloud of error around those estimates.

The 3 reports have the following analytical design characteristics: They appear to be PowerPoint slides. Some tables are difficult to read because of the grid prisons surrounding the entries in the spreadsheet, and it is difficult to make comparisons of numbers across the table. Bullets lists are used throughout, with up to 5 levels of hierarchy on a single page of 10 or 12 lines. Consequently the reasoning is broken up into stupefying fragments both within and between the many slides."

Definitely worth looking at if you are interested in how bad communication can have real-world consequences.

Regards
Keith


--
Keith Soltys
Email: keith -at- soltys -dot- ca - Alternate Email: ksoltys -at- rogers -dot- com
Web: http://www.soltys.ca
Home of Internet Resources For Technical Communicators



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References:
RE: Requirements analysis: From: Diane Boos

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