We know that if people are told a treatment will reduce the risk of a disease by 50 per cent, they make different decisions than if they are told the risk will be reduced from one in 2,000 to one in 3,000.
You need absolute numbers, so here are two questions for your doctor:
If 100 people have this test or treatment, how many of them will have a good result?
If 100 people have this test or treatment, how many will suffer some harmful consequence?