last test3/s1/q23

mzyzhu

Q23, When 100 people who have not used cocaine are tested for cocaine use, on average only 5 will test positive. By contrast. of every 100 people who have used cocaine 99 will test positive. Thus, when a randomly chosen group of people is tested for cocaine use. the vast majority of those who test positive will be people who have used cocaine.

A reasoning error in the argument is that the argument

(C) fails to take into account what proportion of the population have used cocaine.

Can someone explain why the answer is C?