Suppose that 5% of people in society are Solution Lets say there are 100 people in the society so 5 people are nerds now tests accuracy is 85% so if a test shows that dave is a nerd then there is 85% chances of him being amoneg those 5 people and 15% chances of him being those 95 people So dave is right that there is 85 % chance that he may be a nerd.