The overwhelming majority of students did not make sign
errors systematically. This lack of systematic rendering of
sign errors led to uncovering two other causes for sign errors.
One is a confusion in choice and execution of the several
right-hand rules available. Although most students recognized
that the magnetic force is in the direction perpendicular
to the velocity and field after instruction, inconsistent execution
of the proper right-hand rule led to an unsystematic sign
error