Question

1. The center of a normal curve is

a. cannot be negative

b. always equal to zero

c. is the mean of the distribution

d. is the standard deviation

2. In a standard normal distribution, the

a. mean and the standard deviation are both 1 b. mean and the standard deviation can have any value

c. mean is 1 and the standard deviation is 0

d. mean is 0 and the standard deviation is 1

3. Z is a standard normal random variable. What is the value of Z if the area to the right of Z is 0.0122?

a. 1.25

b. -1.25

c. 2.25

d. -2.25

4. Z is a standard normal random variable. The P(-2<Z<1.15)

equals

a. 0.1023

b. 0.0558

c. 0.475

d. 0.0118

5. X is a normally distributed random variable with a mean of 8 and a standard deviation of 3. The probability that X is between 6 and 10 is

a. 0.7486

b. 0.4972

c. 0.6826

d. 0.8413

The weight of football players is normally distributed with a mean of 200 pounds and a standard deviation of 20 pounds.

6. The probability of a player weighing more than 240 pounds is

a. 0.0197

b. 0.9803

c. 0.4803

d. 0.0228

7. Refer to the information in Q6. The probability of a player weighing less than 220 pounds is

a. 0.8413

b. 0.9938

c. 0.4938

d. 0.1587

8. What percent of players weigh between 170 and 230 pounds?

a. 50%

b. 86.64%

c. 68.26%

d. 99.72%

A professor at a local university noted that the grades of her students were normally distributed with a mean of 76 and a standard deviation of 10.

9. The professor has informed us that 16.6 percent of her students received grades of A. What is the minimum score needed to receive a grade of A?

a. 85.7

b. 87.7

c. 88.3

d. 88.7

10. If 12.1 percent of her students failed the course and received F's, what is the maximum score among those who received an F?

a. 63.1

b. 64.3

c. 65.4

d. 66.3

11. A subset of a population selected to represent the population is

a. a subset

b. a small population

c. a sample

d. a parameter

12. The phenomenon that the sampling distribution of the sample mean can be approximated by a normal distribution as the sample size become large is called

a. the neutral theorem

b. the sampling theorem

c. the central limit theorem

d. the normal distribution theorem

13. Which of the following sampling methods does not lead to the samples that can represent population?

a. convenience sampling

b. cluster sampling

c. stratified sampling

d. systematic sampling

14. Stratified random sampling is a method of selecting a sample in which

a. the sample is first divided into strata, and then random samples are taken from each stratum

b. various strata are selected from the sample

c. the population is first divided into strata, and then random samples are drawn from each stratum

d. None of these alternatives is correct

15. Random samples of size 81 are taken from an infinite population whose mean and standard deviation are 200 and 18, respectively. The distribution of the population is unknown. The mean and the standard error of the mean are (assuming infinite population)

a. 200 and 18

b. 81 and 18

c. 9 and 2

d. 200 and 2

16. A population has a mean of 300 and a standard deviation of 18. A sample of 144 observations will be taken. The probability that the sample mean will be between 297 to 303 is (assuming infinite population)

a. 0.4332

b. 0.8664

c. 0.9544

d. 0.0668

17. Doubling the size of the sample will

a. reduce the standard error of the mean to one-half its current value

b. reduce the standard error of the mean to approximately 70% of its current value

c. have no effect on the standard error of the mean

d. double the standard error of the mean

18. A finite population correction factor is needed in computing the standard deviation of the sampling distribution of sample means

a. whenever the population is infinite

b. whenever the sample size is more than 5% of the population size

c. whenever the sample size is less than 5% of the population size

d. The correction factor is not necessary if the population has a normal distribution

In a local university, 40% of the students live in the dormitories. A random sample of 80 students is selected for a particular study. (assuming infinite population)

19. The standard deviation of , known as the standard error of the proportion is approximately

a. 0.5477

b. 5.477

c. 0.05477

d. 54.77

20. Refer to the information in Q19. The probability that the sample proportion (the proportion living in the dormitories) is between 0.30 and 0.50 is

a. 0.4664

b. 0.9328

c. 0.0336

d. 0.0672

Answer 1