Stats Exam 3 Review

It is known that 10% of the calculators shipped from a particular factory are defective. What is the probability that exactly two of five chosen calculators are defective? 0.0729 0.146 0.09 0.07209

0.0729

The probability P(Z < −1.28) is closest to ______ −0.10 0.10 0.20 0.90

0.10

Suppose the round-trip airfare between Boston and Orlando follows the normal probability distribution with a mean of $387.20 and a standard deviation of $68.50. What is the probability that a randomly selected airfare between Boston and San Francisco will be more than $450? 0.2033 0.3369 0.1796 0.0788

0.1796

The probability that a normal random variable is less than its mean is ______. 0.5 Cannot be determined with given information 1.0 0.0

0.5

Suppose the average price of gasoline for a city in the United States follows a continuous uniform distribution with a lower bound of $4.00 per gallon and an upper bound of $4.30 per gallon. What is the probability a randomly chosen gas station charges less than $4.15 per gallon? 0.804 0.500 0.333 0.300

0.500

On a particular production line, the likelihood that a light bulb is defective is 5%. Ten light bulbs are randomly selected. What is the probability that none of the light bulbs will be defective? 0.0746 0.3151 0.5987 0.0105

0.5987

Chauncey Billups, a current shooting guard for the Los Angeles Clippers, has a career free-throw percentage of 89.4%. Suppose he shoots six free throws in tonight's game. What is the standard deviation of the number of free throws that Billups will make? 5.6860 0.5364 0.5686 0.7540

0.7540

The time for a professor to grade a student's homework in statistics is normally distributed with a mean of 14.4 minutes and a standard deviation of 2.4 minutes. What is the probability that randomly selected homework will require less than 18 minutes to grade? 0.1602 0.9332 0.6111 0.7935

0.9332

For a particular clothing store, a marketing firm finds that 16% of $10-off coupons delivered by mail are redeemed. Suppose six customers are randomly selected and are mailed $10-off coupons. What is the expected number of coupons that will be redeemed? 5.04 0.81 0.96 3.42

0.96

Which of the following is not a characteristic of the probability mass function of a discrete random variable X? Multiple Choice A. It is also called the probability density function of X, denoted by f(x). B. It is a list of all possible values x with the associated probabilities P(X = x). C. The sum of probabilities P(X = x) over all possible values x is 1. D. For every possible value x, the probability P(X = x) is between 0 and 1.

A. It is also called the probability density function of X, denoted by f(x).

A continuous random variable has the uniform distribution on the interval [a, b] if its probability density function f(x) ______. A. asymptotically approaches the x axis when x increases to +∞ or decreases to −∞ B. provides probabilities for all x values C. is bell-shaped between a and b D. is constant for all x values between a and b, and 0 otherwise

D. is constant for all x values between a and b, and 0 otherwise

A standard normal variable Z can be transformed to the normally distributed random variable X only if the mean µ is known.

false

According the empirical rule for normally distributed variables, 75% of the values fall within one standard deviation of the mean.

false

The amount of soda consumed by an adult next month is an example of a discrete random variable.

false

A continuous random variable is characterized by uncountable values and can take on any value within an interval.

true

Testing whether computers are infected or not would be best described using binomial probability distribution.

true

Find the z value such that P(Z ≤ z) = 0.5319. z = 0.08 z = 0.0492 z = −0.08 z = 0.0055

z= 0.08

The time of a call to a technical support line is uniformly distributed between 2 and 10 minutes. What are the mean and variance of this distribution? A. 6 minutes and 5.333 minutes B. 6 minutes and 5.333(minutes)2 C. 6 minutes and 2.309 (minutes)2 D. 8 minutes and 2.309 minutes

B. 6 minutes and 5.333(minutes)2

Which of the following can be represented by a discrete random variable? Multiple Choice A. The circumference of a randomly generated circle B. The number of defective light bulbs in a sample of twenty C. The time of a flight between Chicago and New York D. The average distance achieved in a series of long jumps

B. The number of defective light bulbs in a sample of twenty

Heidi's portfolio has an expected annual return at 10%, with an annual standard deviation at 12%. If her investment returns are normally distributed, then in any given year Heidi has approximately ________. A. 99% chance that the actual return will fall within −20% and 40% B. 95% chance that the actual return will fall within −12% and 32% C. 68% chance that the actual return will fall within −2% and 22% D. 50% chance that the actual return will be greater than 12%

C. 68% chance that the actual return will fall within −2% and 22%

Which of the following does not represent a continuous random variable? A. Height of oak trees in a park. B. Time of a flight between Orlando and Houston. C. The number of customer arrivals to a bank between 9 am and 10 am. D. Weight of newborn babies.

C. The number of customer arrivals to a bank between 9 am and 10 am.

Which of the following can be represented by a continuous random variable? Multiple Choice A. the number of heads when tossing a coin B. The number of questions answered correctly by a student on a test C. The time of a flight between Chicago and New York D. The number of arrivals to a drive-through fast food restaurant window in a four-hour period

C. The time of a flight between Chicago and New York

The expected value of a random variable X is referred to as the population mean.

True