if only 50% of the subjects gets HIV does that mean sugar pills have a 50% chance of stopping HIV?
No. It means that the other 50% of the subjects caught HIV from the sugar pill.
...cows alone are causing more global warming than the poorest half of the population of the entire planet...
At least I can eat the cows.
A sine curve goes off to infinity, or at least the end of the blackboard. -- Prof. Steiner