This study was a prospective, randomized, controlled clinical trial. Participant randomization and the use of a control group help randomize confounding bias.Study Execution: Subjects: The study population consisted of 160,921 women who did not have breast cancer in England, Wales, and Scotland . Inclusion criteria were: Women who were age 39-41 and were not currently receiving care for breast cancer. Methods: 160,921 women were randomized by computer to participate in the interventional group or the control group in a 1:2 ratio. Women in the interventional group were offered a mammography once each year and then reinvited back the following year until their 48th birthday. Women in the control group were not offered a mammography. After 7-14 years (with the average at 10.4 years), the researchers would then follow up with the women in both groups by searching through the NHS central register and determine incidence of breast cancer and mortality. Endpoints: The endpoint was determining whether or not mammography done in women in their 40s reduced mortality rate from breast cancer. After 10 years from the start of the trial, the mortality rate due to breast cancer in the interventional group was compared to the rate from the control group. Statistical Analysis: Power was 60% to detect a 20% reduction in breast cancer mortality after a follow up period of 10 years at a 5% significance level. Using a chi-squared test, there was no heterogeneity Results/Discussion:During the first year of the study, 36,538 out of 53,884 women (68%) in the interventional group underwent a mammography. This data was used to calculate the detection rate of breast cancer to be 1.0 per 1,000. In subsequent years, the detection rate increased to a range of 1.0-1.6 per 1,000. 81% of women attended at least one mammography with the average at 4.5 mammographies. When comparing the number of deaths from breast cancer between the interventional and control groups, the 95% confidence interval for the risk ratio was (0.66-1.04) with a center of 0.83. The suggests that the relative reduction in mortality of the interventional group was 17% when compared to the control group. However, this reduction was not statistically significant as the confidence intervals for the risk ratio included 1.Follow up was performed through searching a central database. It was not necessary to physically visit or call each participant. As a result, response bias is decreased and loss of participants was minimized. Conclusion:The trial did not find a statistically significant reduction in breast cancer mortality in women who were offered annual mammograms from age 40 to 48. ANALYSIS OF STUDY 2Study Design:This study is a randomized controlled clinical trial done as a prospective study. To limit confounding bias participant randomization and a control group was used. Median follow up was 24 years.Study Execution:The study consisted of 52,222 women. They were Statistical Analysis: Data was analytics using Poison regression. The varience estimantase were set conservitavely this was to account for the cluster randomization. Results/Discussion:There was 156 deaths due to breast cancer in the control hroup, while the intervention group had only 79. This means there was a 30% reduction in mortality due to the intervention of inviting the women to have mammograms. The the women aged 39-49 the reduction in mortality was 40%.