Two non-scientific friends of mine once tried to figure out what a medical statistician does. After much consideration they came to me with these two things:
1. “If someone’s discovered an antidote [I think they meant a treatment!] to a disease, you test it and see if it is any good?”
2. “You come up with those figures you see in newspapers, things like ‘eating sausages doubles your risk of a heart attack’?”
They actually summarised medical statistics quite well!
My slightly more technical answer would be that medical statistics is the application of statistics to medical and health matters. A medical statistician should have training in the theory and practice of statistics and be able to apply that knowledge to improve global health. For example, a medical statistician should be able to select and use appropriate statistical techniques to analyse medical data, such as data from a clinical trial or an epidemiological study. I.e. we test “antidotes” and come up with figures about the population’s risk… so far I have not investigated sausages though.