Charisma of top-level leaders. Refer to the Academy of Management Journal (August 2015) study of the charisma of top-level leaders, Exercise 11.28 (p. 661). Recall that the researchers used data on 24 US presidential election years to model Democratic vote share (y) as a function of the difference (x) between the Democratic and Republican candidates’ charisma scores. Is there evidence to indicate that the simple linear regression model is statistically useful for predicting Democratic vote share? Test using a = .10.