In view of the high incidence of brain gliomas around the world, Ross Company of the United States has developed a new drug X, which is specially used for postoperative chemotherapy, which is compared with the traditional chemotherapy drug Y in clinical experiments. they were used in two groups of 70 patients with advanced brain gliomas, 35 in each group, the first group was treated with drug Y and the second group was treated with drug X. But two years later, 20 people died in each group. 
Among the living, the first group and the second group were older.
 the new drug X does not have a better effect.