17 March 2003

The short thing to remember on the changes between two polls is: when adding margins of error don't just add, take the square root of the sums of the squares.

(This computation was a little complicated by the fact that for the original polls we want margin of error on both sides, whereas for the difference we're just trying to find out whether the difference is at least say 1 point, not in between 1 and 7 points.)

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