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View Diary: Wherein I Prove* That Keystone XL Pipeline Will Have No Environmental Impacts (90 comments)

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  •  Probabilities are additive in these cases (0+ / 0-)

    If there's a 1% risk per year at each of 26 points on a pipeline, the probability of at least one disaster is 26% per year.

    •  That is simplistic (0+ / 0-)

      Because of the possibility of correlation - that is, if your processes failed on one weld, they are more likely to have failed on the others.

      Common cause failures are the bane of failure analysts, playing a role similar to that of demons in medieval theology.

      Purity is for primaries; in the general, our worst are better than their best.

      by blue aardvark on Thu Mar 06, 2014 at 02:35:59 PM PST

      [ Parent ]

      •  Yes (1+ / 0-)
        Recommended by:
        blue aardvark

        ...and even if they are independent, it's simplistic, as it's multiplicative. If the probability of making a mistake on entering a single digit in a long string is X, the probability of getting the whole string right is 1 minus X to the Nth, where N is the number of digits, I believe.  It gets dangerously low even if you start with a 1% error rate, as N increases.  

        I'm from the Elizabeth Warren wing of the Democratic Party

        by voicemail on Thu Mar 06, 2014 at 03:45:36 PM PST

        [ Parent ]

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