http://homepage.cs.uiowa.edu/~dwjones/voting/cogel/
Jones on Human Factors, Slide 8

 

Relating Instructions to the Task

To Vote, Fill in the Oval, Like this: O
For President
O     BUSH
O     GORE
For President
O   BUSH    (REP)
O   GORE   (DEM)

Most Global precinct-count systems were configured with the target on the right.

 

Invented target rates with good instructions (Global ballots)


Invented target rate with bad instructions (Global ballots)


Over 1,039,000 voters saw clear instructions on Global ballots,
    of them, about 0.006% invented voting targets.
Over 347,000 voters saw instructions reversed from use,
    of them, about 0.09% invented voting targets.

In sum, instruction reversal may have confused 70 voters in the presidential race!