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    Re: Cocked hats, again.
    From: Peter Fogg
    Date: 2007 Mar 20, 08:44 +1100

    On 3/20/07, n s gurnell <nsg1923---.com> wrote:

    It seems that the discussion over cocked hats is cooling off.   May I add a
    quotation from the lips of a famous Master of a famous troopship in World War
    II who would place his hand on the map of the North Atlantic and declare, "I am
    quietly confident that the ship is here and we will make a bold sweep to
    westward" Cheers,nsg

    If you are sailing in a land-locked lake then the chances of your position being outside that lake, in practical terms, are nil.

    However, in statistical terms there will be some chance of this.

    This sort of confusion between statistical theory and the real world leads to nonsensical notions, such as the idea that a position could be "well outside" the position lines that enclose the fix. This fear of the unknown, this dread that the position could be anywhere and must remain unknowable, seems to underlay the fascination with the 25% /  75% proposition.

    This is just another example of how statistics is a good servant but a bad master.

    Relax, folks. Chill, dudes and dudesses. By all means do what you can to reduce error, then accept that your fix represents the best approximation of your position that you can achieve.

    If you can and want to, calculate the standard deviation of multiple sights and construct shadow position lines that will enclose about a 70% and then about a 90% chance that this larger shape encloses the position.

    This is, apparently, statistically quite valid and converts your allegedly 25% chance of the shape containing the position to a 70% or 90% chance. However the fix; the only indicative point of position that can be rationally derived, remains in the same place.


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