Speaking precisely

Let's Be PreciseIT PAYS TO BE CAREFUL.  In statistics, precision differs from accuracy; but sometimes folks might state a precision and give the impression that they've stated an accuracy.  "This poll has a margin of error of ±3%" is just one example.  I recall one polling season when a host of polls cited such a margin, but cited also estimated outcomes that differed by far more than that margin.  All but one of the seven or eight polls gave margins of ±3% around the wrong answer.*

(*The polls were each taken the day before the election by different organizations, and the election results were used as the standard reference.)

Remainder of the essay is here:


The images below the cut have been uploaded here because for some reason LJ will let me pull images from my computer while Blogger will not.  At least not today.