Many leadership theories have provided evidence that leaders affect group success rather than the success of particular individuals. So it is irrelevant to analyze the effects of supervisor traits on the attitudes of individuals whom they supervise. Instead, assessment of leadership effectiveness should occur only at the group level. Which of the following would it be most useful to establish in order to evaluate the argument? ['Whether some types of groups do not need supervision in order to be successful in their endeavors', "Whether individuals' attitudes toward supervisors affect group success", "Whether any of the leadership theories in question hold that leaders should assess other leaders' attitudes", "Whether it is possible to assess individual supervisees' attitudes toward their supervisors without thereby changing those attitudes"]