Management professors at columbia university examined the relationship between assertiveness and leadership (journal of personality and social psychology, february 2007). the sample was comprised of 388 people enrolled in a full-time mba program. based on answers to a questionnaire, the researchers measured two variables for each subject: assertiveness score (x) and leadership ability score (y). a quadratic regression model was fit to the data with the following results: independent variable b estimate t-value p-valuex 0.57 2.55 0.01x^2 -0.88 -3.97 < 0.01model r^2 = 0.12conduct a test of overall model utility. use a=0.05