Use the following results from a test for marijuana use, which is provided by a

Question

Use the following results from a test for marijuana use, which is provided by a certain drug testing company. Among 143 subjects with positive test results, there are 21 false positive results. Among 154 negative results, there are 5 false negative results. Complete parts (a) through (c). a. How many subjects were included in the study? The total number of subjects in the study was b. How many subjects did not use marijuana? A total of subjects did not use marijuana. c. What is the probability that a randomly selected subject did not use marijuana? The probability that a randomly selected subject did not use marijuana is (Do not round until the final answer. Then round to three decimal places as needed.)

Explanation / Answer

number of subjects test positive ia 143

number of subjects test negative is 154

a) total number of subjects = 297

b) number of students didnot use marijuna is

given there are false positive is 21

number of subjects that test are negative 154

and number of false negative 5

21+154 - 5 =170

c) the probability that a randomly selected subject did not use marijuana

is

number of students didnot use marijuna /   total number of subjects   

170/297=0.5723

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