### Home > CCA2 > Chapter Ch12 > Lesson 12.1.2 > Problem 12-35

A number of states are considering legislation that calls for people to get mandatory drug testing in order to qualify for public assistance money. Some argue that mandatory testing of welfare recipients would jeopardize the livelihood of many people who do not have substance abuse problems and is therefore an unwarranted invasion of their privacy.

Consider a hypothetical situation. Suppose that the currently used test for illegal drugs is

Make a model for this situation.

Make a two-way table or tree diagram.

Users/Non-users and Positive drug test/Negative drug testHow does the proportion of people who are using drugs compare with the proportion of people who will be told they are using drugs but really are not?

The proportion of people using drugs is

^{23}/_{1000}.

Use your model to find the proportion of non-users that test positive (situation D).If a randomly tested recipient’s test comes back positive, what is the probability that he or she is

*not*actually using drugs?Write up your statistical conclusions.

Use your answers to parts (b) and (c) to justify your conclusions.

Are the test results mathematically independent of using or not using drugs? How could you check this? Explain.

Does the accuracy of the drug test depend on whether or not someone is a user?