Name:    AP Statistics Chapter 6 Practice MC Test

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

1.

Which of the following random variables should be considered continuous?
 a. The number of CD’s a randomly chosen person has b. The number of sisters a randomly chosen person has c. The number of goals scored in a randomly chosen soccer game d. The number of tacos ordered by a randomly chosen Del Taco customer. e. None of the above

2.

A psychologist studied the number of puzzles subjects were able to solve in a five-minute period while listening to soothing music.  Let X be the number of puzzles completed successfully by a subject.  X had the following distribution:

X            1     2     3     4
Probability      0.2   0.4   0.3   0.1

Using the above data, the mean µ of X is
 a. 2.0 b. 2.3 c. 2.5 d. 3.0 e. The answer cannot be computed from the information given.

3.

A random variable X has a probability distribution as follows:

X      0      1      2      3_
P(X)      2k      3k      13k      2k

Then the probability that P(X = 2) is equal to
 a. 0.90. b. 0.25. c. 0.65. d. 0.15. e. 1.00.

4.

Suppose X is a random variable with mean µ.  Suppose we observe X many times and keep track of the average of the observed values.  The law of large numbers says that
 a. The value of µ will get larger and larger as we observe X. b. As we observe X more and more, this average and the value of µ will get larger and larger. c. This average will get closer and closer to µ as we observe X more and more often. d. As we observe X more and more, this average will get to be a larger and larger multiple of µ. e. None of the above

5.

A factory makes silicon chips for use in computers.  It is known that about 90% of the chips meets specifications.  Every hour a sample of 18 chips is selected at random for testing.  Assume a binomial distribution is valid.  Suppose we collect a large number of these samples of 18 chips and determine the number meeting specifications in each sample.  What is the approximate mean of the number of chips meeting specifications?
 a. 16.20 b. 1.62 c. 4.02 d. 16.00 e. The answer cannot be computed from the information given.

6.

Twenty percent of all trucks undergoing a certain inspection will fail the inspection.  Assume that trucks are independently undergoing this inspection, one at a time.  The expected number of trucks inspected before a truck fails inspection is
 a. 2 b. 4 c. 5 d. 20 e. The answer cannot be computed from the information given

7.

Two percent of the circuit boards manufactured by a particular company are defective.  If circuit boards are randomly selected for testing, the probability it takes 10 circuit boards to be inspected before a defective board is found is
 a. .0167 b. .9833 c. 0.1829 d. 0.8171 e. The answer cannot be computed from the information given

8.

Two percent of the circuit boards manufactured by a particular company are defective.  If circuit boards are randomly selected for testing, the probability that the number of circuit boards inspected before a defective board is found is greater than 10 is
 a. 1.024 ´ 10^7 b. 5.12 ´ 10^7 c. 0.1829 d. 0.8171 e. The answer cannot be computed from the information given

9.

It has been estimated that about 30% of frozen chickens contain enough salmonella bacteria to cause illness if improperly cooked. A consumer purchases 12 frozen chickens. What is the probability that the consumer will have exactly 6 contaminated chickens?
 a. 0.961 b. 0.118 c. 0.882 d. 0.039 e. 0.079

10.

It has been estimated that about 30% of frozen chickens contain enough salmonella bacteria to cause illness if improperly cooked. A consumer purchases 12 frozen chickens. What is the probability that the consumer will have more than 6 contaminated chickens?
 a. 0.961 b. 0.118 c. 0.882 d. 0.039 e. 0.079