Use these results from the “1-Panel-THC” test for marijuana use, which is provided by the company Drug Test Success: Among 143 subjects with positive test results, there are 24 false positive results; among 157 negative results, there are 3 false negative results.
(Hint: Construct a table similar to Table 4-1, which is included with the Chapter Problem.)
1) Screening for Marijuana Use
a.
How many subjects are included in the study?
b.
How many subjects did not use marijuana?
c.
What is the probability that a randomly selected subject did not use marijuana?
2) Screening for Marijuana Use
If one of the test subjects is randomly selected, find the probability that the subject tested positive or used marijuana.
3) Screening for Marijuana Use
If one of the test subjects is randomly selected, find the probability that the subject tested negative or did not use marijuana.
4) Screening for Marijuana Use
If one of the test subjects is randomly selected, find the probability that the subject actually used marijuana. Do you think that the result reflects the marijuana use rate in the general population?
5) Screening for Marijuana Use
Find the probability of a false positive or false negative. What does the result suggest about the test’s accuracy?
6) Screening for Marijuana Use
Find the probability of a correct result by finding the probability of a true positive or a true negative. How does this result relate to the result from Exercise 37?