What is one problem that might commonly occur when one is bartering? a) someone wants to trade a valuable item for a less valuable one. b) two people have different ideas about the value of an item. c) someone wants to barter a good in exchange for a service. d) two people want to trade items of equal or nearly equal value.

answer:

d. because dr. laguardia selected a widely used measure, his study generalizes to has strong external validity. external validity has limited external validity. other applications of this measure.

the widely used measure that he applied to his experiment was the benton facial recognition test. it employed on to football players and as result, only players who suffered brain concussions did not pas this test. and although it has an external validity, it is limited because it isn't general to apply to other population.