# EBook Problems Distrib RV

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## 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