1. For a normal distribution, a negative value of z indicates
| a. a mistake has been made in computations, because z is always positive. |
| b. the z is to the left of the mean. |
| c. the z is to the right of the mean. |
| d. the area corresponding to the z is negative |
Correct Response
b
2. z is a standard normal random variable. The P (1.41 ≤ z ≤ 2.85) equals
| a. 0.4207 |
| b. 0.9185 |
| c. 0.0771 |
| d. 0.4978 |
Correct Response
c
3. A professor at a local university noted that the exam grades of her students were normally distributed with a mean of 73 and a standard deviation of 11. The professor has informed us that 7.93 percent of her students received grades of A. What is the minimum score needed to receive a grade of A?
| a. 100.00 |
| b. 93.2 |
| c. 90.51 |
| d. 88.51 |
Correct Response
d
4. For a continuous random variable x, the probability density function f(x) represents
| a. the area under the curve to the right of x. |
| b. the height of the function at x. |
| c. the probability at a given value of x. |
| d. the area under the curve at x. |
Correct Response
b
5. The exponential probability distribution is used with
| a. a continuous random variable. |
| b. an approximation of the binomial probability distribution. |
| c. a discrete random variable. |
| d. any probability distribution with an exponential term. |
Correct Response
a
6. z is a standard normal random variable. The P (1.20 ≤ z ≤ 1.85) equals
| a. 0.4678 |
| b. 0.8527 |
| c. 0.0829 |
| d. 0.3849 |
Correct Response
c
7. The weight of football players is normally distributed with a mean of 200 pounds and a standard deviation of 25 pounds. The probability of a player weighing more than 241.25 pounds is
| a. 0.0495 |
| b. 0.4505 |
| c. 0.9010 |
| d. 0.9505 |
Correct Response
a
8. An experiment consists of measuring the speed of automobiles on a highway by the use of radar equipment. The random variable in this experiment is speed, measured in miles per hour. This random variable is a
| a. nominal random variable. |
| b. discrete random variable. |
| c. continuous random variable. |
| d. ordinal random variable. |
Correct Response
c
9. For the standard normal probability distribution, the area to the right of the mean is
| a. 1. |
| b. 0.5. |
| c. 3.09. |
| d. 1.96. |
Correct Response
b
10. Given that z is a standard normal random variable. What is the value of z if the area to the left of z is 0.9382?
| a. 1.8 |
| b. 2.1 |
| c. 1.77 |
| d. 1.54 |
Correct Response
d
11. Given that z is a standard normal random variable, what is the probability that z ≥ -2.12?
| a. 0.966 |
| b. 0.9830 |
| c. 0.4830 |
| d. 0.017 |
Correct Response
b
12. Given that z is a standard normal random variable, what is the probability that -2.08 ≤ z ≤ 1.46?
| a. 0.9091 |
| b. 0.4279 |
| c. 0.0533 |
| d. 0.4812 |
Correct Response
a
13. If arrivals follow a Poisson probability distribution, the time between successive arrivals must follow
| a. an exponential probability distribution. |
| b. a Poisson probability distribution. |
| c. a normal probability distribution. |
| d. a uniform probability distribution. |
Correct Response
a
14. A continuous random variable is uniformly distributed between a and b. The probability density function between a and b is
| a. (b – a). |
| b. 1/(b – a). |
| c. (a – b). |
| d. zero. |
Correct Response
b
15. z is a standard normal random variable. What is the value of z if the area between –z and z is 0.754?
| a. 1.16 |
| b. 0.123 |
| c. 0.377 |
| d. 2.16 |
Correct Response
a
16. What is the probability that x is less than 5, given the function below?
f(x) =(1/10) e–x/10 x ≥ 0
| a. 0.9393 |
| b. 0.6065 |
| c. 0.3935 |
| d. 0.0606 |
Correct Response
c
17. The uniform, normal, and exponential distributions
| a. are all the same distributions. |
| b. can be either continuous or discrete, depending on the data. |
| c. are all continuous probability distributions. |
| d. are all discrete probability distributions. |
Correct Response
c
18. The travel time for a college student traveling between her home and her college is uniformly distributed between 40 and 90 minutes. The probability that she will finish her trip in 80 minutes or less is
| a. 0.2 |
| b. 0.8 |
| c. 0.02 |
| d. 1.00 |
Correct Response
b
19. z is a standard normal random variable. The P(-1.96 ≤ z ≤ -1.4) equals
| a. 0.475 |
| b. 0.8942 |
| c. 0.0558 |
| d. 0.4192 |
Correct Response
c
20. x is a normally distributed random variable with a mean of 12 and a standard deviation of 3. The probability that x equals 19.62 is
| a. 0.0055 |
| b. 0.4945 |
| c. 0.9945 |
| d. 0.000 |
Correct Response
d
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