A veterinarian does research on the causes of enteroliths, stones that develop in the colon of horses. She suspects that feeding alfalfa might be a cause. To investigate that suspicion, she selects five horses that are known to have enteroliths (e) and compares the number of flakes of alfalfa they have eaten over a month with the number of flakes eaten by five horses free of enteroliths (h). The researcher should test which of the hypotheses?.