ProbabilityBayes' Theorem and Applications (ISS (Statistical Services) Statistics Paper I (New 2016 MCQ Pattern)): Questions 4  5 of 5
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Question number: 4
» Probability » Bayes' Theorem and Applications
Question
Suppose a certain drug test is 99 % sensitive and 99 % specific, that is, the test will correctly identify a drug user as testing positive 99 % of the time, and will correctly identify a nonuser as testing negative 99 % of the time. Let’s assume a corporation decides to test its employees for drug use, and that only 0.5 % of the employees actually use the drug. The probability that, given a positive drug test, an employee is actually a drug user is conducted using Bayes’ theorem. Can we say Bayes’ theorem gives correct result?
Choices
Choice (4)  Response  

a.  Information insufficient 

b.  Yes always 

c.  Not always 

d.  Can’t make any claim 

Question number: 5
» Probability » Bayes' Theorem and Applications
Question
Suppose there is a school with 40 % boys and 60 % girls as its students. The female students wear trousers or skirts in equal numbers; the boys all wear trousers. An observer sees a (random) student from a distance, and what the observer can see is that this student is wearing trousers. What is the probability this student is a girl?
Choices
Choice (4)  Response  

a.  0.552 

b.  0.250 

c.  0.428 

d.  Question does not provide sufficient data or is vague 
