# ISS (Statistical Services) Statistics Paper I (New 2016 MCQ Pattern): Questions 275 - 277 of 472

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## Question number: 275

» 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 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

### 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

### 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 |