Maybe make the test takers take the Sakirnova test and test them on their functions and see which function is their strongest and then analyze their chart. Or maybe have them read up on their function to see if they really do feel connected to the function's description. I don't...
Actually, in this test the introverted/extroverted thing is more about what you do to recharge, rather than how shy you are. Basically, an introvert gets tired of being around people and needs to spend some time alone to reflect, while an extrovert is motivated by being around other people...