A psychologist wants to determine which type of psychotherapy is most effective in helping people overcome their fear of heights. She randomly assigns clients with a fear of heights to one of three forms of psychotherapy (i.e., psychodynamic, rational-emotive, or behavioral modification) or a control condition. Each client in a treatment condition receives ten sessions with a trained therapist; those in the control group receive no treatment. All clients are then taken to the fifteenth floor of an office building and asked to stand next to a floor-to-ceiling window and rate their anxiety on a 20-point scale (20 = strongest fear; 0 = no fear). The researcher selects an alpha of .05. Below are the data for each group.

Group 1: Control 20, 14, 18, 16, 17, 17

Group 2: Psychodynamic 20, 9, 10, 15, 15, 15

Group 3: Rational-Emotive 18, 7, 15, 9, 11, 12

Group 4: Behavior Modification 15, 5, 6, 13, 12, 9

What is the null and alternative hypothesis