Atenolol is a beta block used to lower heart rate, and in turn lower systolic blood pressure. you are conducting research on atenolol to see if it really does lower the heart rate of your patients. a sample of 19 patients was taken and you took their heart rate before and after 2 week of being on atenolol. assuming you subtracted the before HR from the after HR what notation is correct for this test. please explain process