# EBook Problems Distrib RV

## Contents

## EBook Problems Set - Random Variables

### Problem 1

The probability model below describes the number of repair calls that an appliance repair shop may receive during an hour:

Repair calls | 0 | 1 | 2 | 3 |

P(x) | 0.1 | 0.3 | 0.4 | 0.2 |

The probability that the number of repair calls is at least 2 is:

- Choose one answer.

*(a) 0.8*

*(b) 0.2*

*(c) 0.4*

*(d) 0.6*

### Problem 2

In a litter of seven kittens, three are female. You pick two kittens at random. The probability model for the number of male kittens is:

Number males | 0 | 1 | 2 |

Probability | 0.143 | 0.571 | 0.286 |

The expected number of males is:

- Choose one answer.

*(a) 0.64*

*(b) 1.7*

*(c) 1.14*

*(d) 2.1*

### Problem 3

Let X represent a discrete random variable that takes any of the values and probabilities given below:

X | -2 | 5 | 6 |

P(X) | 0.4 | 0.4 | __ |

The probability for X = 6 is missing. What is it?

- Choose one answer.

*(a) It cannot be determined from the information given*

*(b) 0.2*

*(c) 0.6*

*(d) 2.3*

### Problem 4

The manager of a stock room in a factory knows from her study of records that the daily demand for a certain tool has the following probability model:

Demand | 0 | 1 | 2 |

Probability | 0.1 | 0.5 | 0.4 |

Suppose it costs the factory $10 each time the tool is used. Find the variance of the daily cost of using the tool.

- Choose one answer.

*(a) 13*

*(b) 41*

*(c) 1.3*

*(d) 10*

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