Assertiveness and leadership. Management professors at Columbia University examined the relationship between assertiveness and leadership (Journal of Personality and Social Psychology, Feb. 2007). The sample represented 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 lead- ership ability score (). A quadratic regression model was fit to the data with the following results: Independent Variable B Estimate t-value p-value x .57 -,088 2.55 -3.97 ,01 <.01 x2 Model R2 ,12 a, Conduct a test of overall model utility, Use a = .05. b: The researchers hypothesized that leadership ability will increase at a decreasing rate with assertiveness. Set up the null and alternative hypotheses to test this theory. c. Use the reported results to conduct the test, part b. Give your conclusion (at a .05) in the words of the problem