Name:    CP Stats - Discrete Random Variables -  Practice MC Questions

Multiple Choice
Identify the choice that best completes the statement or answers the question.

A small bakery has determined the following probability distribution for the number of cheesecakes that they sell in a given day.

 Number Sold 0 1 2 3 4 Prob (Number Sold) .05 .20 .30 .35 .10

1.

Find the probability that the bakery sells at least 1 cheesecake in a day.
 a) 0.05 b) 0.1 c) 0.55 d) 0.9 e) 0.95

2.

Find the probability that the bakery sells more than 2 cheesecakes in a day.
 a) 0.1 b) 0.45 c) 0.55 d) 0.75 e) 0.9

3.

Find the mean number of cakes the bakery can expect to sell in a day.
 a) 2 b) 2.25 c) 2.5 d) 2.75 e) 3

4.

Which of the following random variables is geometric?
 a) The number of times I have to roll a single die to get two 6’s. b) The number of cards I deal from a well-shuffled deck of 52 cards until I get a heart. c) The number of digits I read in a table of the random digits until I find a 7. d) The number of 7’s in a row of 40 random digits. e) The number of 6’s I get if I roll a die 10 times.

5.

A test for extrasensory perception (ESP) involves asking a person to tell which of 5 shapes - a circle, star, triangle, diamond or heart - appears on a hidden computer screen. On each trial, the computer is equally likely to select any of the 5 shapes. Suppose researchers are testing a person who does not have ESP and so is just guessing on each trial. What is the probability the person guesses that the first 4 shapes incorrectly but gets the fifth correct?
 a) b) c) d) e)

6.

To calculate the binomial probability of 5 successes out of 8 trials when success in any given trial has probability 0.65, use the calculation
 a) d) b) e) c)

7.

Russell’s parents roll a fair, six-sided die every morning, and if the result is a 1 or 2, they pack yogurt in his lunch. What is the probability that he gets yogurt on exactly 2 of the 5 school days next week?
 a) 0.111 b) 0.4 c) 0.165 d) 0.329 e) 0.671

The U.S. Department of Education conducted a study in 2003 that revealed that 14% of  U.S. adults lack basic literacy skills (they cannot read or write at a functional level).

8.

Suppose that 20 U.S. adults are selected at random and contacted by telephone for a news article related to this study. What is the probability that at least 1 of these people is not literate?
 a) 0.049 b) 0.14 c) 0.159 d) 0.841 e) 0.951

9.

Suppose that U.S. adults are selected at random and contacted by telephone for a news article related to this study. The author of the article will call someone until they find someone who is not literate. What is the probability that the author will need to talk to 10 people in order to find such a person?
 a) 0.036 b) 0.042 c) 0.049 d) 0.057 e) 0.066

10.

Suppose that U.S. adults are selected at random and contacted by telephone for a news article related to this study. The author of the article will call someone until they find someone who is not literate. What is the expected number of people that the author will talk to in order to find such a person?
 a) 7 b) 7.14 c) 8 d) 8.2 e) 14