Use the following results from a test for marijuana use, which is provided by a
ID: 2947248 • Letter: U
Question
Use the following results from a test for marijuana use, which is provided by a certain drug testing company. Among 144 subjects with positive test results, there are 27 false positive results; among 152 negative results, there are 3 false negative results. If one of the test subjects is randomly selected, find the probability that the subject tested negative or did not use marijuana. (Hint: Construct a table.) The probability that a randomly selected subject tested negative or did not use marijuana is (Do not round until the final answer. Then round to three decimal places as needed.)Explanation / Answer
The Contingency table is
P( Negative or didnot use marijuana) =
P(negative)+P(did not use marijuana)- P(negative and didnot use marijuana)
= (152+30-3)/296 =179/296 =0.605
Use Marijuana (True) Did not use Marijuana (False) Total Positive 144-27 =117 27 144 Negative 152-3 =149 3 152 Total 266 30 296