Question 1

While conducting experiments, a marine biologist selects water depths from a uniformly distributed collection that vary between 2.00 m and 7.00 m. What is the probability that a randomly selected depth is less than 3.60 m?

Accepted Answer

A)  .72 
B)  .80 
C)  .46 
D)  .32

Question 2

During the past six months, 73.2 percent of U.S. households purchased sugar. Assume that these expenditures are approximately normally distributed with a mean of $8.22 and a standard deviation of $1.10. Ninety-nine percent of the households spent less than what amount?

Accepted Answer

A)  $5.66 
B)  $10.78 
C)  $6.81 
D)  $9.63

Question 3

Which of the following is a continuous distribution?

Accepted Answer

A)  Poisson 
B)  hypergeometric 
C)  exponential 
D)  binomial

Question 4

The average time an individual reads online national news reports is 49 minutes. Assume the standard deviation is 16 minutes and that the times are normally distributed. For the 10 percent who spend the most time reading national news online, how much time do they spend?

Accepted Answer

A)  > 11.72 
B)  > 28.52 
C)  > 86.28 
D)  > 69.50

Question 5

For a continuous distribution, the exact probability of a particular value is zero.

Accepted Answer

A) True 
 B)False

Question 6

The weight of a product is normally distributed with a mean of 4 ounces and a variance of .25 squared ounces. What is the probability that a randomly selected unit from a recently manufactured batch weighs more than 5 ounces?

Accepted Answer

A)  .0228 
B)  .9772 
C)  .000 
D)  1.00

Question 7

The grade a student received on an examination was transformed to a z value, which was negative. Therefore, we know that the student scored

Accepted Answer

A)  higher than 16 percent of the class. 
B)  higher than 45 percent of the class. 
C)  above the first quartile. 
D)  below the mean. 
E)  lower than 16 percent of the class.

Question 8

What is the probability that a standard normal random variable will be between .3 and 3.2?

Accepted Answer

A)  .6179 
B)  .3814 
C)  .3808 
D)  .9993

Question 9

A plant manager knows that the number of boxes of supplies received weekly is normally distributed with a mean of 200 and a standard deviation of 20. What percentage of the time will the number of boxes received in a week exceed 200?

Accepted Answer

A)  100% 
B)  25% 
C)  0% 
D)  50%

Question 10

During the past six months, 73.2 percent of U.S. households purchased sugar. Assume that these expenditures are approximately normally distributed with a mean of $8.22 and a standard deviation of $1.10. Find the probability that a household spent more than $16.00 on sugar.

Accepted Answer

A)  1.00 
B)  .00 
C)  .50 
D)  .98

Question 11

Find z when the area to the right of z is .1314.

Accepted Answer

A)  1.12 
B)  .55 
C)  −.55 
D)  −1.12

Question 12

The thickness of a randomly selected metal piece is a ________ random variable.

Accepted Answer

A)  Poisson 
B)  continuous 
C)  discrete 
D)  binomial

Question 13

An aptitude test has a mean score of 80 and a standard deviation of 5. The population of scores is normally distributed. What proportion of tests has scores over 90?

Accepted Answer

A)  .9772 
B)  .0228 
C)  .9544 
D)  .0456

Question 14

A probability distribution that describes the time or space between successive occurrences of an event is a(n) ________ probability distribution.

Accepted Answer

A)  binomial 
B)  uniform 
C)  exponential 
D)  normal

Question 15

The weight of a product is normally distributed with a mean of 4 ounces and a variance of .25 squared ounces. The company wants to classify the unit as a scrap in a maximum of 1 percent of the units if the weight is below a desired value. Determine the desired weight such that no more than 1 percent of the units are below it.

Accepted Answer

A)  3.360 
B)  3.680 
C)  2.835 
D)  3.418

Question 16

The average time an individual reads online national news reports is 49 minutes. Assume the standard deviation is 16 minutes and that the times are normally distributed. What is the probability someone will spend no more than 30 minutes reading online national news reports?

Accepted Answer

A)  .1175 
B)  .0301 
C)  .8830 
D)  .9699

Question 17

Find z when the area between 0 and z is .4750.

Accepted Answer

A)  −1.96 
B)  1.96 
C)  .68 
D)  −.68

Question 18

The time between breakdowns of an alarm system is exponentially distributed with mean 10 days. What is the probability that there is less than 1 breakdown on a given day?

Accepted Answer

A)  .9048 
B)  .3679 
C)  .0952 
D)  .000

Question 19

The cashier service time at the local branch of the Rivertown bank has an exponential distribution with a mean of 2.5 minutes. What is the probability that the service time is between 2 and 4 minutes?

Accepted Answer

A)  .2488 
B)  .4493 
C)  .2019 
D)  .2474 
E)  .1170

Question 20

For a continuous distribution, P(X ≤ 100) = P(X < 100).

Accepted Answer