Wednesday, January 21, 2015

Space Shuttle Certainty


So.. I've thought about making this required reading for my team:
http://science.ksc.nasa.gov/shuttle/missions/51-l/docs/rogers-commission/Appendix-F.txt

The link is to Richard Feynman's appendix to the Rogers Commission report on why the Challenger Space Shuttle failed.  Though not the best read on statistical uncertainty, the point is simple: an inaccurate accounting of statistical uncertainty led to 7 deaths and a major setback in the US space program.  I think people serious about creating mathematical models should read this, but the important part is this:

There were a cloud of points some twice above, and some twice below the fitted curve, so erosions twice predicted were reasonable from that cause alone. Similar uncertainties surrounded the other constants in the formula, etc., etc. When using a mathematical model careful attention must be given to uncertainties in the model.
Effectively the space shuttle failed largely because a statistical estimate of wear/tolerance was treated as a deterministic mathematical equation, and no one accounted for uncertainty in multiple dependent parameter estimates.

Though most models aren't matters of life and death, the assessment of uncertainty is something we can't ignore if we are to make accurate predictions.

Feynman ends his appendix with a slap to NASA management.. though not relevant to this blog, is worth remembering:
For a successful technology, reality must take precedence over public relations, for nature cannot be fooled.


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