I. Multiple Choice: Select the best answer from the given choice. Use UPPERCASE letters only. (2

points each)

1. Which statement is not true about confidence intervals?

A. A confidence interval is an interval of values computed from sample data that is likely to

include the true population value.

B. An approximate formula for a 95% confidence interval is a sample estimate margin of

error.

C. A confidence interval between 20% and 40% means that the population parameter lies

between 20% and 40%.

D. A 99% confidence interval procedure has a higher probability of producing intervals that will

include the population parameter that a 95% confidence interval procedure.

2. A randomly selected sample of 400 students at a university with 15-week semesters was asked

whether or not they think the semester should be shortened to 14 weeks (with longer classes).

Forty six percent (46%) of the 400 students surveyed answered "yes". Which of the following

statements about the number 46% is correct?

A. It is a sample statistic.

B. It is a population parameter.

C. It is a margin of error.

D. It is a standard error.

3. Pulse rates of adult men are approximately normal with a mean of 70 and a standard deviation

of 8. Which choice correctly describes how to find the probability of men that have a pulse rate

greater than 78?

A. Find the area to the left of z = 1 under the standard normal curve.

B. Find the area between z = 1 & z = 1 under a standard normal curve.

C. Find the area to the right of z = 1 under a standard normal curve.

D. Find the area to the right of z = 1 under a standard normal curve.

4. Which of the following is an example of a point estimate?

A. Population mean

B. Sample mean

C. Population variance

D. Population standard deviation

5. In a sample of size 25, in order to compute any sample statistic, how many sample values are

free to vary?

A. 25

B. 24

C. 50

D. 1

6. The z - value that is used to construct a 95% confidence interval is:

A. 1.654

B. 1.96

C. 1.28

D. 2.575

7. The z - value which is used to construct a 99% confidence interval is:

A. 2.575

B. 1.28

C. 1.96

D. 1.654

8. Which of the following is NOT a property of the student's t - distribution?

A. Its exact shape is characterized by the degrees of freedom.

B. As the sample size grows, it gradually approaches the normal distribution.

C. It is symmetric.

D. All of the above are properties of the t - distribution.

9. Which of the following is FALSE?

A. Alpha is the proportion in the tails of the distribution which outside of the confidence

interval.

B. In practice, the population mean is an unknown quantity that is to be estimated.

C. There is a different z - value used for each level of alpha.

D. It is possible to construct a 100% confidence interval estimate for the population mean.

10. The alpha value for a 98% confidence interval would be ____.

A. 0.10

B. 0.02

C. 0.20

D. 0.05

11. When estimating the population mean with a small sample, the t - distribution may be used with

____ degrees of freedom.

A. n 2

B. n 1

C. n

D. n + 1

12. The t - value that would be used to construct a 99% confidence interval for the mean with a sample of size n = 17 would be ______.

A. 2.921

B. 2.567

C. 2.583

D. 2.898

13. Inferential statistics is the _________.

A. process of using a population parameter to estimate the values for sample statistics

B. process of using sample statistics to estimate population parameters

C. process which allows the researcher to determine the exact values for population

parameters

D. process that eliminates the problem of sampling error

14. In the formula for the confidence interval, z/2 is part of the formula. What does the subscript /2 refer to?

A. The level of confidence

B. The level of significance

C. The probability that the confidence interval will not contain the population mean

D. The area in the lower tail or upper tail of the sampling distribution of the sample mean

15. After constructing a confidence interval estimate for a population mean, you believe that the

interval is useless because it is too wide. In order to correct this problem, you need to _______.

A. increase the population standard deviation

B. increase the sample size

C. increase the level of confidence

D. decrease the sample size

16. In a hypothesis test,

A. the null hypothesis is what we are trying to prove.

B. the alternative hypothesis is always assumed to be true.

C. the alternative hypothesis is accepted unless there is a sufficient evidence to say otherwise.

D. the null hypothesis is not rejected unless there is a sufficient evidence to reject it.

17. Nestor Milk Powder is sold in packets with an advertised mean weight of 1.5 kgs. The standard

deviation is known to be 184 grams. A consumer group wishes to check the accuracy of the

advertised mean and takes a sample of 52 packets finding an average weight of 1.49 kgs. What

is the set of hypotheses that should be used to test the accuracy of advertised weight?

A. H0; = 1.5; Ha: 1.5

B. H0; = 1.5; Ha: < 1.5

C. H0; x = 1.49; Ha: x 1.49

D. H0; x = 1.5; Ha: x < 1.5

18. Mr. Russo believes that the mean income of lawyers is now more than Php 3 Million per year.

Which is the correct set of hypotheses to test this belief?

A. H0; 3; Ha: < 3

B. H0; 3; Ha: > 3

C. H0; = 3; Ha: 3

D. H0; < 3; Ha: 3

19. Suppose a businessperson wishes to open a store in a local shopping center only if there is a

strong evidence that the average number of people in the center is greater than 5000 per day.

The null hypothesis will be

A. H0: 5000

B. H0: > 5000

C. H0: 5000

D. H0: < 5000

20. In hypothesis testing,

A. rejecting the null hypothesis might lead to a type II error.

B. a type II error occurs whenever the null hypothesis is accepted.

C. Both A and B are correct.

D. Both A and B are incorrect.

21. What is the smallest sample size required to provide a 95% confidence interval for a mean, if it

is important that the interval be no longer than 1 cm? You may assume that the population is

normal with variance of 9 cm2.

A. 1245

B. 35

C. 95

D. 139

II. Complete the table below by graphing the curve and stating the correct decision (accept Ho or

reject H0) in each item. (18 points)

Given Graph Decision

H0: = 100

Ha: 100

z computed: = 1.312

z critical: = 1.257

H0: 100

Ha: > 100

z computed: = 2.312

z critical: = 2.125

H0: 100

Ha: < 100

z computed: = 1.312

z critical: = 1.736