According to a recent warning from the FDA, grain-free food might be giving dogs a life-threatening heart problem called dilated cardiomyopathy, or DCM. Scientists interested in studying this link were trying to see if there was a difference in the average blood pressure of dogs on grain-free dog food vs the average blood pressure of dogs on food that includes grains. To minimize variation in subjects, scientists measured the initial blood pressure of 30 dogs while each was still on a grain-free diet, and then took a second measurement 8 weeks after each dog was switched to a diet that included grains. What hypothesis test would be appropriate for analyzing the above scenario