Mendoza et al. (2009) introduced a coin-rotation task as a convenient test of motor dexterity. it involves timed completion of twenty 180° rotations of a nickel using the thumb, index, and middle fingers. research participants' results on the coin-rotation task are compared with their results on a test of grip strength (a measure of another construct: global upper-extremity strength). the correlation between the coin-rotation task and the grip strength task were found to be not statistically significant. this comparison provides support for which type of measurement validity?