Business Statistics
Quiz #4
1. A confidence interval can be described as ___________________.
A.
B.
C.
D.
X plus or minus the margin of error.
X bar plus or minus the margin of error.
Sigma plus or minus the margin of error.
S plus or minus the margin of error.
2. Which of the following best articulates the level of significance?
A. 1- the confidence level.
B. It is the amount of error you are willing to accept in creating a confidence
interval.
C. It is how confident you want to be in creating your confidence interval.
D. Two of the above.
3. The confidence interval will tell you which of the following:
A.
B.
C.
D.
The probability that X bar lies within your stated interval.
All possible values for .
The probability that  lies within the defined interval.
The probability that the sample standard deviation is equal to .
4. Derek Zoolander samples 100 Orange Mocha Frappuccinos and finds they have an
average of 500 calories each. The population standard deviation is 100 and the sample
standard deviation is 110. What is the confidence interval if you have a .1 level of
significance?
A. 493- 507
B. 456-544
C. 400-600
D.484-516
5. What happens to your confidence interval if the confidence level increases?
A. The confidence interval will expand.
B. The confidence interval will contract.
C. The confidence interval will remain the same.
6. What happens to your confidence interval if the sample size increases?
A. The confidence interval will expand.
B. The confidence interval will contract.
C. The confidence interval will remain the same.
7. You want to construct a margin of error with a z score of 1 at your desired significance
level, a sample mean of 300, a population standard deviation of 100, a sample standard
deviation of 80, and a sample size of 100. What is the margin of error?
A. 10
B. 8
C. 30
D. 16
8. Why is the z-score for a confidence interval calculated at /2 rather than ?
A.
B.
C.
D.
Because the distribution is not assumed to be normal.
Because the confidence interval is defined in one tail of the distribution.
Because the confidence interval is twice as large as .
Because the interval must account for both tails of the distribution.
9. You have a sample of 36 spider-monkeys. The average life span according to your
sample is 100 days. The sample has a standard deviation of 12. You want to be 90%
confident in your interval. What is your confidence interval?
A.
B.
C.
D.
90-110
97-103
80-120
87-113
10. From the data in problem 9, what would be your answer if your sample size were 16?
A.
B.
C.
D.
90-110
97-103
87-113
95-105