Question 1

What is the area under the normal curve between z = 0.0 and z = 1.79?

Accepted Answer

A) 0.4633 
B) 0.0367 
C) 0.9599 
D) 0.0401

Question 2

What is the area under the normal curve between z = −1.0 and z = −2.0?

Accepted Answer

A) 0.0228 
B) 0.3413 
C) 0.1359 
D) 0.4772

Question 3

Consider a standard normal random variable z. What is the value of z if the area to the right of z is 0.2643?

Accepted Answer

A) 0.72 
B) 0.28 
C) 1.46 
D) 0.63

Question 4

If an average of 12 12 customers are served per hour,what is the probability that the next customer will arrive in 6 minutes or less?

Accepted Answer

A) 0.61 
B) 0.30 
C) 0.70 
D) 0.39

Question 5

The time to fly between New York City and Chicago is uniformly distributed with a minimum of 120 minutes and a maximum of 150 minutes. What is the distribution's mean?

Accepted Answer

A) 120 minutes 
B) 150 minutes 
C) 135 minutes 
D) 270 minutes

Question 6

Some normal probability distributions are positively skewed.

Accepted Answer

A) True 
 B)False

Question 7

Ball-Bearings,Inc. produces ball bearings automatically on a Kronar BBX machine. For one of the ball bearings,the mean diameter is set at 20.00 mm (millimeters). The standard deviation of the production over a long period of time was computed to be 0.150 mm. What percent of the ball bearings will have diameters of 20.27 mm or more?

Accepted Answer

A) 41.00% 
B) 12.62% 
C) 3.59% 
D) 85.00%

Question 8

For a uniformly distributed random variable,x,P(x)= 1/(b − a).

Accepted Answer

A) True 
 B)False

Question 9

The mean score of a college entrance test is 500; the standard deviation is 75. The scores are normally distributed. What percent of the students scored below 320?

Accepted Answer

A) About 50.82% 
B) About 34.13% 
C) About 7.86% 
D) About 0.82%

Question 10

A group of normal distributions can have equal arithmetic means but different standard deviations.

Accepted Answer

A) True 
 B)False

Question 11

The average starting salary of individuals with a master's degree in statistics is normally distributed with a mean of $48,000 and a standard deviation of $6,000. What is the probability that a randomly selected individual with a master's in statistics will get a starting salary of at least $55,000?

Accepted Answer

A) 0.121 
B) 0.891 
C) 0.379 
D) 0.098

Question 12

The total area of a normal probability distribution is ________.

Accepted Answer

A) between −3.0 and 3.0 
B) 1.00 
C) dependent on a value of z 
D) approximated by the binomial distribution

Question 13

A binomial distribution has 100 trials (n = 100)with a probability of success of 0.25 (π = 0.25). We would like to find the probability of 34 or more successes using the normal distribution to approximate the binomial. Applying the continuity correction factor,what z-score should be used?

Accepted Answer

A) 2.079 
B) 2.194 
C) 1.963 
D) 0.25

Question 14

The shape of any uniform probability distribution is ________.

Accepted Answer

A) negatively skewed 
B) positively skewed 
C) rectangular 
D) bell-shaped

Question 15

The normal distribution can be used to approximate a binomial distribution when nπ is less than 5.

Accepted Answer

A) True 
 B)False

Question 16

A new extended-life light bulb has an average life of 750 hours,with a standard deviation of 50 hours. If the life of these light bulbs approximates a normal distribution,about what percent of the distribution will be between 600 hours and 900 hours?

Accepted Answer

A) 95% 
B) 68% 
C) 34% 
D) 99.74%

Question 17

The standard normal distribution is a special normal distribution with a mean of 0 and a standard deviation of 1.

Accepted Answer

A) True 
 B)False

Question 18

The average score of 100 students taking a statistics final was 70 with a standard deviation of 7. Assuming a normal distribution,what test score separates the top 25% of the students from the lower 75% of students?

Accepted Answer

A) 70.00 
B) 74.69 
C) 65.31 
D) 75.25

Question 19

The average score of 100 students taking a statistics final was 70 with a standard deviation of 7. Assuming a normal distribution,what is the probability that a student scored greater than 65?

Accepted Answer

A) 0.2611 
B) 0.2389 
C) 0.7611 
D) −0.714

Question 20

The number of different standard normal distributions is unlimited.

Accepted Answer

A) True 
 B)False

Exam 7: Continuous Probability Distributions

What is the area under the normal curve between z = 0.0 and z = 1.79?

What is the area under the normal curve between z = −1.0 and z = −2.0?

Consider a standard normal random variable z. What is the value of z if the area to the right of z is 0.2643?

If an average of 12 12 customers are served per hour,what is the probability that the next customer will arrive in 6 minutes or less?

The time to fly between New York City and Chicago is uniformly distributed with a minimum of 120 minutes and a maximum of 150 minutes. What is the distribution's mean?

Some normal probability distributions are positively skewed.

For a uniformly distributed random variable,x,P(x)= 1/(b − a).

The mean score of a college entrance test is 500; the standard deviation is 75. The scores are normally distributed. What percent of the students scored below 320?

A group of normal distributions can have equal arithmetic means but different standard deviations.

The average starting salary of individuals with a master's degree in statistics is normally distributed with a mean of $48,000 and a standard deviation of $6,000. What is the probability that a randomly selected individual with a master's in statistics will get a starting salary of at least $55,000?

The total area of a normal probability distribution is ________.

A binomial distribution has 100 trials (n = 100) with a probability of success of 0.25 (π = 0.25) . We would like to find the probability of 34 or more successes using the normal distribution to approximate the binomial. Applying the continuity correction factor,what z-score should be used?

The shape of any uniform probability distribution is ________.

The normal distribution can be used to approximate a binomial distribution when nπ is less than 5.

A new extended-life light bulb has an average life of 750 hours,with a standard deviation of 50 hours. If the life of these light bulbs approximates a normal distribution,about what percent of the distribution will be between 600 hours and 900 hours?

The standard normal distribution is a special normal distribution with a mean of 0 and a standard deviation of 1.

The average score of 100 students taking a statistics final was 70 with a standard deviation of 7. Assuming a normal distribution,what test score separates the top 25% of the students from the lower 75% of students?

The average score of 100 students taking a statistics final was 70 with a standard deviation of 7. Assuming a normal distribution,what is the probability that a student scored greater than 65?

The number of different standard normal distributions is unlimited.