To find out whether a new serum will arrest leukemia, 9 mice, which have all reached an advanced stage of the disease, are selected. Five mice receive the treatment and 4 do not. The survival times in...

Extracted text: To find out whether a new serum will arrest leukemia, 9 mice, which have all reached an advanced stage of the disease, are selected. Five mice receive the treatment and 4 do not. The 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 Assume equal variances. Can we conclude that the serum is effective at 0.05 level of significance?