AP Statistics Chapter 6 Random Variables

The probability that an American household will have at least 2 cars is...

• 0.55

• 0.35

• 0.45

• 0.93

What's the expected number of cars in a randomly selected American household?

• 1.00

• 1.75

• 1.84

• 2.00

How would you interpret the expected value in number 3?

• The maximum number of cars for the household is Exp(C).

• The average number of cars for the household is Exp(C).

• If we randomly select many households, the average number of cars per household will be approximately by Exp(C).

• If we randomly select many households, the average number of cars per household will vary approximately by Exp(C).

The number of calories in a 1-ounce serving of a certain breakfast cereal is a random variable with mean 110 and standard deviation 10. The number of calories in a cup of whole milk is a random variable with mean 140 and standard deviation 12. For breakfast, you eat 1 ounce of the cereal and 1/2 cup of whole milk. Let T be the random variable that represents the total number of calories in this breakfast. The standard deviation of T is...

• 22

• 16

• 15.62

• 11.66

A certain vending machine offers 20-ounce bottles of soda for $1.50. The number of bottles X bought from the machine on any day is a random variable with mean 50 and standard deviation 15. Let the random variable Y equal the total revenue from this machine on a given day. Assume the machine works properly and that no sodas are stolen from the machine. What are the mean and standard deviation of Y?

• Mean Y = $1.50 and St. Dev Y = $22.50

• Mean Y = $1.50 and St. Dev Y = $33.75

• Mean Y = $75 and St. Dev Y = $18.37

• Mean Y = $75 and St. Dev Y = $22.50

• Mean Y = $75 and St. Dev Y = $33.75

A binomial event has n = 60 trials. The probability of success on each trial is 0.4. Let X be the count of successes of the event during the 60 trials. What are mean X and standard deviation X?

• 24; 3.79

• 24; 14.4

• 4.9; 3.79

• 4.9; 14.4

The GPA of students who take the AP Statistics exam are approximately normally distributed with a mean of 3.4 with a standard deviation of 0.3. What is the probability that a student selected at random from this group has a GPA lower than 3?

• 0.0918

• 0.4082

• 0.9082

• -0.0918

The probability of x, the number of tires needing replacement on a randomly selected automobile checked at a certain inspection station is given in the following table. What is the standard deviation of X?

• 1.2

• 2.52

• 1.58

The number of vehicles leaving a highway at a certain exit during a particular time period has a distribution that is approximately normal with mean value 500 and standard deviation 75. What is the probability that the number of cars exiting during this period is at least 650?

• 0.977

• 0.023

• 0.477

The probability that an American household will have at most 3 cars is...

• 0.93

• 0.20

• 0.13

• 0.07