# ISS (Statistical Services) Statistics Paper I (New 2016 MCQ Pattern): Questions 275 - 277 of 471

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## Question number: 275

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MCQ▾

### 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 non-user 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.

Not always

b.

Yes always

c.

Can’t make any claim

d.

Information insufficient

## Question number: 276

» Probability » Probability Distributions » Negative Binomial

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MCQ▾

### Question

In a sequence of independent Bernoulli trails, if denotes the number of failures before (fixed) success, then the expected value of will be ________

### Choices

Choice (4) Response

a.

b.

c.

d.

None of the above

## Question number: 277

» Probability » Probability Distributions » Poisson

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MCQ▾

### Question

Twenty sheets of copper alloy were examined for surface flaws. The frequency of the number of sheets with a given number of flaws per sheet was as follows:

 Number of flaws Frequency 0 4 1 3 2 5 3 2 4 4 5 1

What is the probability of finding a sheet chosen at random which contains 3 or more surface flaws?

### Choices

Choice (4) Response

a.

b.

c.

d.

Question does not provide sufficient data or is vague