In this homework activity, students use a BBC article to identify and evaluate the elements of an experiment. The article "Circumcision 'reduces HIV risk'" provides a detailed report of an experiment in South Africa that examines the effect of circumcision on HIV rates. Students read the article and use it to identify experimental concepts taught in class. They are also prompted to comment on the ethics of such an experiment. Click the "Resources" tab for the worksheet. The article can be found 4371384.stm .