Download Ch 10 Rev Ques

1.
Module 10 Review Questions
You want to compute a 95% confidence interval for a population mean. Assume that the population
standard deviation is known to be 10 and the sample size is 50. The value of z* to be used in this
calculation is
(a) 1.960
(b) 1.645
(c) 1.7507
(d) 2.0537
(e) None of the above. The answer is
.
2.
You want to estimate the mean SAT score for a population of students with a 90% confidence interval.
Assume that the population standard deviation is s = 100. If you want the margin of error to be
approximately 10, you will need a sample size of
(a) 16
(b) 271
(c) 38
(d) 1476
(e) None of the above. The answer is
.
3.
A significance test gives a P-value of 0.04. From this we can
(a) Reject H0 at the 1% significance level
(b) Reject H0 at the 5% significance level
(c) Say that the probability that H0 is false is 0.04
(d) Say that the probability that H0 is true is 0.04
(e) None of the above. The answer is
4.
.
A significance test was performed to test the null hypothesis H0: µ = 2 versus the alternative Ha: µ ≠ 2.
The test statistic is z = 1.40. The P-value for this test is approximately
(a) 0.16
(b) 0.08
(c) 0.003
(d) 0.92
(e) 0.70
(f) None of the above. The answer is
.
5. You have measured the systolic blood pressure of a random sample of 25 employees of a company located
near you. A 95% confidence interval for the mean systolic blood pressure for the employees of this company is
(122, 138). Which of the following statements is a correct interpretation of this interval?
(a) Ninety-five percent of the sample of employees has a systolic blood pressure between 122 and 138.
(b) Ninety-five percent of the population of employees has a systolic blood pressure between 122 and 138.
(c) If the procedure were repeated many times, 95% of the resulting confidence intervals would contain the
population mean systolic blood pressure.
(d) The probability that the population mean blood pressure is between 122 and 138 is .95.
(e) If the procedure were repeated many times, 95% of the sample means would be between 122 and 138.
(f) None of the above. The answer is
.
6. An analyst, using a random sample of n = 500 families, obtained a 90% confidence interval for mean
monthly family income for a large population: ($600, $800). If the analyst had used a 99% confidence
coefficient instead, the confidence interval would be:
(a)
(b)
(c)
(d)
(e)
Narrower and would involve a larger risk of being incorrect
Wider and would involve a smaller risk of being incorrect
Narrower and would involve a smaller risk of being incorrect
Wider and would involve a larger risk of being incorrect
Wider but it cannot be determined whether the risk of being incorrect would be larger or smaller
7. To determine the reliability of experts used in interpreting the results of polygraph examinations in criminal
investigations, 280 cases were studied. The results were:
True Status
Examiner’s decision
Innocent
Guilty
Guilty
9
125
Innocent
131
15
If the hypotheses were H0: suspect is innocent vs. Ha: suspect is guilty, then we could estimate the
probability of making a Type II error as:
(a) 15/280
(b) 9/280
(c) 15/140
(d) 9/140
(e) 15/146
8. Which of the following are correct?
I. The power of a significance test depends, in part, on the alternative value of the parameter.
II. The probability of a Type II error is equal to the significance level of the test.
III. Type I and Type II errors only make sense when a significance level has been chosen in advance.
(a) I and II only
(b) I and III only
(c) II and III only
(d) I, II, and III
(f) None of the above gives the complete set of true responses.
9. A 95% confidence interval for µ is calculated to be (1.7, 3.5). It is now decided to test the hypothesis H0: µ =
0 vs. Ha: µ ≠ 0 at the α = 0.05 level, using the same data as was used to construct the confidence interval.
(a) We cannot test the hypothesis without the original data.
(b) We cannot test the hypothesis at the α = 0.05 level since the α = 0.05 test is connected to the 97.5%
confidence interval.
(c) We can only make the connection between hypothesis tests and confidence intervals if the sample sizes
are large.
(d) We would reject H0 at level α = 0.05.
(e) We would fail to reject H0 at level α = 0.05.
10. In a statistical test for the equality of a mean, such as H0 µ = 10, if α = 0.05,
(a)
(b)
(c)
(d)
(e)
95% of the time we will make an incorrect inference
5% of the time we will say that there is a real difference when there is no difference
5% of the time we will say that there is no real difference when there is a difference
95% of the time the null hypothesis will be correct
5% of the time we will make a correct inference
Answers:
1. a
2. b
3. b
4. a
5. c
6. b
7. c
8. b
9. d
10. b