Dolon Web Security Consultants requries all job applicants to submit to a test for illegal drugs. If the applicant has used illegal drugs, the test has 90 percent chance of a positive result. If the applicant has not used illegal drugs, the test has an 85 percent chance of negative result. Actually, 4 percent of the job applicants have used illegal drugs. If an applicant has a positive test, what is the probability that he or she has actually used illegal drugs

20 percent

Step-by-step explanation:

P(Used illegal drugs) = 4%

P(+ test | Used illegal drugs) = 90%        

P(- test | Has not Used illegal drugs) = 85%      

P(+ test ) =

P(+ test and Used illegal drugs) + P(+ test and Has not used Illegal drugs) =

[ P(+ test | Used illegal drugs) * P(Used illegal drugs) ] + [ P(+ test | Has not Used illegal drugs) * P(Has not Used illegal drugs) ],

since

P(+ test and Used illegal drugs) = P(+ test | Used illegal drugs) * P(Used illegal drugs)

P(+ test and Has not used illegal drugs) =P(+ test | Has not Used illegal drugs) * P(Has not Used illegal drugs)  

Thus,

P(+ test ) =  

[ (90%)(4%) ]  +  [ (100% - 85%)(100% - 4%) ] =

0.9*.04 + .15*.96 =

0.18

and,

we want  

P(Used illegal drugs | + test),

and

P(Used illegal drugs and + test) = P(+ test | Used illegal drugs) * P(Used illegal drugs) = 0.9*0.04 = 0.036

and we have that

P(Used illegal drugs and + test) = P(Used illegal drugs | + test) * P(+test)

so that

0.036 = P(Used illegal drugs | + test) * 0.18

so that

P(Used illegal drugs |+ test) =

0.036 / 0.18 =

0.2 =    

20 percent

i would say c is the best answer, hope it's right!

good luck! =)

cutie~

the central idea is that:

individuals should refuse to cooperate with institutions they believe unjust.

thoreau felt  that governments were more often agents of corruption than justice, even democracies, and that just because the majority feels a certain way does not make it just or correct in absolute terms. he uses the fact that slavery exists in our democracy to support this idea.

he goes on to say that, as a result, people should live true to their own internal laws regarding right and wrong, as a product of reflection and a moral life, rather than following every law that society imposes. 

step-by-step explanation: