To nd out whether a new serum will arrest leukemia, 9 mice, all with an advanced stage of the disease, are selected. Five mice receive the treatment and 4 do not. Survival times, in years, from the time the experiment commenced are as follows: Treatment 2.1 5.3 1.4 4.6 0.9 No Treatment 1.9 0.5 2.8 3.1 At the 0.05 level of signicance, can the serum be said to be eective? Assume the two populations to be normally distributed with equal variances