# stat

1

Marks: 1

W4-01. Suppose x is a random variable best described by a uniform probability distribution with c EQUAL 30 and d EQUAL 90. Find P(30 â‰¤ x â‰¤ 45).

Choose one answer.

a. 0.15

b. 0.35

c. 0.25

d. 0.025

Question 2

Marks: 1

W4-12. Which geometric shape is used to represent areas for a uniform distribution?

Choose one answer.

a. Rectangle

b. Triangle

c. Bell curve

d. Circle

Question 3

Marks: 1

W4-17. Find a value of the standard normal random variable z, called z0, such that P(-z0â‰¤ z â‰¤ z0) EQUAL 0.98.

Choose one answer.

a. 2.33

b. 1.96

c. .99

d. 1.645

Question 4

Marks: 1

W4-03. Suppose x is a random variable best described by a uniform probability distribution with c EQUAL 20 and d EQUAL 60. Find P(x > 60).

Choose one answer.

a. 0.4

b. 0.5

c. 1

d. 0

Question 5

Marks: 1

W4-02. Suppose x is a random variable best described by a uniform probability distribution with c EQUAL 10 and d EQUAL 90. Find P(x < 42).

Choose one answer.

a. 0.04

b. 0.5

c. 0.4

d. 0.32

Question 6

Marks: 1

W4-20. A physical fitness association is including the mile run in its secondary-school fitness test. The time for this event for boys in secondary school is known to possess a normal distribution with a mean of 440 seconds and a standard deviation of 50 seconds. Find the probability that a randomly selected boy in secondary school can run the mile in less than 325 seconds.

Choose one answer.

a. .0107

b. .4893

c. .5107

d. .9893

Question 7

Marks: 1

W4-08. The diameters of ball bearings produced in a manufacturing process can be described using a uniform distribution over the interval 3.5 to 5.5 millimeters. What is the probability that a randomly selected ball bearing has a diameter greater than 4.6 millimeters?

Choose one answer.

a. 2

b. 0.8364

c. 0.5111

d. 0.45

Question 8

Marks: 1

W4-06. Suppose x is a random variable best described by a uniform probability distribution with c EQUAL 3 and d EQUAL 9. Find the value of a that makes the following probability statement true: P(3.5 â‰¤ x â‰¤ EQUAL 0.5.

Choose one answer.

a. 6.5

b. 6

c. 4

d. 1.2

Question 9

Marks: 1

W4-07. High temperatures in a certain city for the month of August follow a uniform distribution over the interval 68Â°F to 90Â°F. What is the probability that the high temperature on a day in August exceeds 73Â°F?

Choose one answer.

a. 0.0455

b. 0.2273

c. 0.462

d. 0.7727

Question 10

Marks: 1

W4-05. Suppose x is a random variable best described by a uniform probability distribution with c EQUAL 3 and d EQUAL 5. Find the value of a THAT makes the following probability statement true: P(x â‰¤ EQUAL 0.75.

Choose one answer.

a. 4.7

b. 4.5

c. 3.5

d. 1.5

Question 11

Marks: 1

W4-19. For a standard normal random variable, find the probability that z exceeds the value -1.65.

Choose one answer.

a. 0.5495

b. 0.4505

c. 0.0495

d. 0.9505

Question 12

Marks: 1

W4-13. Suppose x is a uniform random variable with c EQUAL 40 and d EQUAL 70. Find the standard deviation of x.

Choose one answer.

a. Ïƒ EQUAL 3.03

b. Ïƒ EQUAL 1.58

c. Ïƒ EQUAL 8.66

d. Ïƒ EQUAL 31.75

Question 13

Marks: 1

W4-09. A machine is set to pump cleanser into a process at the rate of 7 gallons per minute. Upon inspection, it is learned that the machine actually pumps cleanser at a rate described by the uniform distribution over the interval 6.5 to 9.5 gallons per minute. What is the probability that at the time the machine is checked it is pumping more than 8.0 gallons per minute?

Choose one answer.

a. .50

b. .25

c. .7692

d. .667

Question 14

Marks: 1

W4-15. After a particular heavy snowstorm, the depth of snow reported in a mountain village followed a uniform distribution over the interval from 15 to 22 inches of snow. Find the standard deviation of the snowfall amounts.

Choose one answer.

a. 1.42 inches

b. 18.5 inches

c. 2.02 inches

d. 4.08 inches

Question 15

Marks: 1

W4-11. The age of customers at a local hardware store follows a uniform distribution over the interval from 18 to 60 years old. Find the probability that the next customer who walks through the door exceeds 50 years old. Round to the nearest ten-thousandth.

Choose one answer.

a. 0.3600

b. 0.7619

c. 0.8333

d. 0.2381

Question 16

Marks: 1

W4-14. Suppose a uniform random variable can be used to describe the outcome of an experiment with outcomes ranging from 30 to 80. What is the mean outcome of this experiment?

Choose one answer.

a. 55

b. 30

c. 80

d. 60

Question 17

Marks: 1

W4-16. Use the standard normal distribution to find P(-2.25 < z < 0).

Choose one answer.

a. .5122

b. .4878

c. .6831

d. .0122

Question 18

Marks: 1

W4-10. A machine is set to pump cleanser into a process at the rate of 9 gallons per minute. Upon inspection, it is learned that the machine actually pumps cleanser at a rate described by the uniform distribution over the interval 8.5 to 11.5 gallons per minute. Find the probability that between 9.0 gallons and 10.0 gallons are pumped during a randomly selected minute.

Choose one answer.

a. 0

b. 0.33

c. 1

d. 0.67

Question 19

Marks: 1

W4-04. Suppose x is a uniform random variable with c EQUAL 20 and d EQUAL 60. Find P(x > 44).

Choose one answer.

a. 0.4

b. 0.9

c. 0.6

d. 0.1

Question 20

Marks: 1

W4-18. Find a value of the standard normal random variable z, called z0, such that P(z â‰¤ z0) EQUAL 0.70.

Choose one answer.

a. .47

b. .98

c. .53

d. .81