Breast Cancer What is the preferred treatment for breast cancer that is detected in its early stages? The most common treatment was once surgical removal of the breast (treatment A). It is now usual to remove only the tumour and nearby lymph nodes, followed by radiation (treatment B). To study whether these treatments differ in their effectiveness, a medical team examines the records of 25 large hospitals and compares the survival times after surgery of women who have had treatment A to those who have had treatment B. Question 4 Breast Cancer What is the explanatory variable in the breast cancer study? Presence of breast cancer Survival time Hospital Type of surgery/follow-up O Surgical team 0.5 pts Question 5 Breast Cancer What is the response variable in the breast cancer study? Survival time Hospital Type of surgery/follow-up Surgical team Presence of breast cancer Question 6 Breast Cancer Is the breast cancer study an experiment or observational study? Observational Experiment 0.5 pts 0.5 pts