1.If X is a normal random variable such that X ~ N (100,20),the standard deviation of the distribution is

A..100

B.4.47

C.20

D.10

2.Number of emergency cases occurs in a day at a hospital follows a Poisson distribution with mean 5.5.

What is the probability that there will be 8 emergency cases in a period of 2days?

A.

0.0618

B.

0.0849

C.

0.0888

D.

0.0143

3. The weights of college students are normally distributed with mean 68kg and standard deviation 3kg.

A student is chosen at random.What is the probability that the weight of the student is between 70and 72kg?

A.

0.7473

B.

0.6660

C.

0.9087

D.

0.1610

4. The lifetime of a type of light bulbs produced by a factory is normally distributed with mean 1400hours and standard deviation 80hours.

If 5%of the light bulbs last for less than k hours,find the value of k.

A.

1358.41

B.

1441.59

C.

1268.4

D.

1531.6

5.If X is a Poisson random variable such that X~P₀(2.5),what is the standard deviation of X?

A.

1.581

B.

2.50

C.

6.25

D.

0.082

6.Number of cars arrived at a car wash center follows a Poisson distribution with an average of 3per hour.

What is the probability that there will be more than 2 cars arrive in one hour?

A.

0.2240

B.

0.3528

C.

0.6721

D.

0.5768

7.Number of calls received by a customer service center of an airline company follows a Poisson distribution with mean 2.8 per day.

Find the probability that the customer service center will receive at most 2 calls in one day.

A.

0.3218

B.

0.2311

C.

0.4695

D.

0.5305

8.The diameter of washer produced by a machine is normally distributed with mean 5.02 mm and standard deviation 0.05 mm.

Find the probability that a washer selected at random will have a diameter more than 5.05mm.

A.

0.7257

B.

0.6000

C.

0.2743

D.

0.4000

9.If X is a normal random variablesuch that X~ N (75, 8), what percentage of values will be more than the mean of the distribution?

A.

68%

B.

8%

C.

75%

D.

50%

10.If X is Poisson random variable such that X~P₀(3.8), what is the value of E(X)?

A.

0.02

B.

0.09

C.

1.95

D.

3.80