Breast cancer is one of the most common malignancies among women in Canada and the U.S. If it is detected early enough-before the cancer spreads chances of successful treatment are much better. Do screening pro- grams speed up detection by enough to matter? Many studies have examined this question. The Canadian National Breast Cancer Study was a randomized controlled experiment on mammography, that is, x-ray screening for breast cancer. The study found no benefit from screening. (The benefit was measured by com- paring death rates from breast cancer in the treatment and control groups.) Dr. Daniel Kopans argued that the randomization was not done properly: in- stead of following instructions, nurses assigned high risk women to the treat- ment group. Would this bias the study? If so, would the bias make the benefit from screening look bigger or smaller than it really is? Explain your answer. Ular werkt.