Most scientific theories are based on assumptions. they are known as hypotheses, which are tested. That is what science is mostly about.

Statistical analysis has been proven to be useful in medicine, i.e. not "stupid". There is a branch of medicine known as epidemiology which is very helpful in terms of public medicine, which involves a lot of statistics.

http://en.wikipedia.org/wiki/Epidemiology

E.g. statistics will tell you how many people in a population you need immunise/vaccinate in order to create 'herd immunity'.

It's not stupid at all, it's essential in learning and understanding about epidemics and pandemics and other public health issues.