To compare two treatments for solid tumors, researchers inoculated two groups
of rats with a highly malignant neoplasm. After the rats were randomized into the
treatments, the survival (days) was observed as follows:
Group 1, Drug A: 12, 16, 16, 18+, 19+, 20,28
Group 2, Drug B: 10, 14, 15, 18, 18,20+, 21
(a) Plot the survival curve for each group.
(b) Compute the product limit estimates of these curves and the corresponding
standard errors for each observed time.
(c) Use a statistical test to compare the survival curves.
(d) Comment on the results.