Question 1

The mean amount spent by a family of four on food is $500 per month with a standard deviation of $75. Assuming that the food costs are normally distributed, what is the probability that a family spends less than $410 per month?

Accepted Answer

A) 0.2158 
B) 0.8750 
C) 0.0362 
D) 0.1151

Question 2

In a standard normal distribution, µ = ______ and σ = _____.

Accepted Answer

The answer of In a standard normal distribution, µ =...

Question 3

About ______% of the area under the normal curve is within plus two and minus two standard deviations of the mean.

Accepted Answer

The answer of About ______% of the area under the...

Question 4

For a normal distribution, what is the likelihood (expressed as a percentage) that a random variable is within plus and minus two standard deviations of the mean?

Accepted Answer

A) 68.26% 
B) 99.74% 
C) 34.13% 
D) 95.44%

Question 5

The shape of the uniform distribution is ___________.

Accepted Answer

The answer of The shape of the uniform distribution is...

Question 6

The proportion of the area under a normal curve that is to the right of z = -1.71 is _______.

Accepted Answer

The answer of The proportion of the area under a...

Question 7

The proportion of the area under a normal curve that is to the left of z = 1.40 is _______.

Accepted Answer

The answer of The proportion of the area under a...

Question 8

When referring to the normal probability distribution, there is not just one; there is a "family" of normal probability distributions.

Accepted Answer

A) True 
 B)False

Question 9

The seasonal output of a new experimental strain of pepper plants was carefully weighed. The mean weight per plant is 15.0 pounds, and the standard deviation of the normally distributed weights is 1.75 pounds. Of the 200 plants in the experiment, how many produced peppers weighing between 13 and 16 pounds?

Accepted Answer

A) 100 
B) 118 
C) 197 
D) 53

Question 10

For the standard normal distribution, the z-score that corresponds with the first quartile is ________.

Accepted Answer

The answer of For the standard normal distribution, the z-score...

Question 11

The upper and lower limits of a uniform probability distribution are __________.

Accepted Answer

A) Positive and negative infinity 
B) Plus and minus three standard deviations 
C) 0 and 1 
D) The maximum and minimum values of the random variable

Question 12

Two business major students, in two different sections of an economics class, were comparing test scores. The following shows the sections' mean and standard deviation.  The student in section 1 scored 84, while the student in section 2 scored 75. The student from section _____ scored better compared than the rest of the section.

Accepted Answer

The answer of Two business major students, in two different...

Question 13

Customers of the Key Refining Company charge an average of $70 per month. The distribution of amounts charged is approximately normal, with a standard deviation of $10. What is the probability of selecting a credit card customer at random and finding the customer charged between $70 and $83?

Accepted Answer

A) 0.1962 
B) 0.4032 
C) 0.3413 
D) 0.4750

Question 14

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 probability that a flight is less than 135 minutes?

Accepted Answer

A) 1.00 
B) 0.50 
C) 0.25 
D) 0.00

Question 15

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 16

For the normal distribution, the mean plus and minus two standard deviations will include about what percent of the observations?

Accepted Answer

A) 50% 
B) 99.7% 
C) 95% 
D) 68%

Question 17

The annual commissions per salesperson employed by a retailer of mobile communication devices averaged $40,000, with a standard deviation of $5,000. What percent of the salespersons earn between $32,000 and $42,000?

Accepted Answer

A) 60.06% 
B) 39.94% 
C) 34.13% 
D) 81.66%

Question 18

The weight of a bag of corn chips is normally distributed with a mean of 22 ounces and a standard deviation of 0.5 ounces. The probability that a bag of corn chips weighs more than 23 ounces is ____.

Accepted Answer

The answer of The weight of a bag of corn...

Question 19

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) 99.47%

Question 20

The standard normal probability distribution is unique because it has _________.

Accepted Answer

A) A mean of 1 and any standard deviation 
B) Any mean and a standard deviation of 1 
C) A mean of 0 and any standard deviation 
D) A mean of 0 and a standard deviation of 1

Exam 7: Continuous Probability Distributions