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Ch 10-12a Review
1. A 95% confidence interval for the mean µ of a population is computed from a random sample and found
to be 9 ± 3. We may conclude
A) that there is a 95% probability that µ is between 6 and 12.
B) that there is a 95% probability that the true mean is 9 and there is a 95% chance that the true margin
of error is 3.
C) that if we took many, many additional random samples and from each computed a 95% confidence
interval for µ, approximately 95% of these intervals would contain µ.
D) all of the above.
2. The records of all 100 postal employees at a postal station in a large city showed that the average amount
of time these employees had worked for the U.S. Postal Service was x = 8 years. Assume that we know
that the standard deviation of the amount of time U.S. Postal Service employees have spent with the
Postal Service is approximately normal with standard deviation σ = 5 years. A 95% confidence interval
for the mean time µ the population of U.S. Postal Service employees has spent with the postal service
based on these data is
A) 8 ± 0.82.
B) 8 ± 0.98.
C) 8 ± 9.80.
D) not trustworthy.
3. The scores of a certain population on the Wechsler Intelligence Scale for Children (WISC) are thought to
be normally distributed with mean µ and standard deviation σ = 10. A simple random sample of 10
children from this population is taken, and each is given the WISC. The 95% confidence interval
x ± 1.96
10
for µ is computed from these scores. A histogram of the 10 WISC scores is given below.
10
Based on this histogram, we would conclude that
A) the 95% confidence interval computed from these data is very reliable.
B) the 95% confidence interval computed from these data is not very reliable.
C) the 95% confidence interval computed from these data is actually a 99% confidence interval.
D) the 95% confidence interval computed from these data is actually a 90% confidence interval.
4. A 90% confidence interval for the mean µ of a population is computed from a random sample and is
found to be 9 ± 3. Which of the following could be the 95% confidence interval based on the same data?
A) 9 ± 2.
B) 9 ± 3.
C) 9 ± 4.
D) Without knowing the sample size, any of the above answers could be the 95% confidence interval.
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Ch 10-12a Review
5. An agricultural researcher plants 25 plots with a new variety of corn. The average yield for these plots is
x = 150 bushels per acre. Assume that the yield per acre for the new variety of corn follows a normal
distribution with unknown mean µ and standard deviation σ = 10 bushels per acre. A 90% confidence
interval for µ is
A) 150 ± 2.00.
B) 150 ± 3.29.
C) 150 ± 3.92.
D) 150 ± 32.90.
6. An agricultural researcher plants 25 plots with a new variety of corn. A 90% confidence interval for the
average yield for these plots is found to be 162.72 ± 4.47 bushels per acre. Which of the following would
produce a confidence interval with a smaller margin of error than this 90% confidence interval?
A) planting only five plots rather than 25, since five are easier to manage and control.
B) planting 100 plots rather than 25.
C) computing a 99% confidence interval rather than a 90% confidence interval; the increase in
confidence indicates that we have a better interval.
D) none of the above.
Use the following to answer questions 7-8:
You measure the heights of a random sample of 400 high school sophomore males in a Midwestern state. The
sample mean is x = 66.2 inches. Suppose that the heights of all high school sophomore males follow a normal
distribution with unknown mean µ and standard deviation σ = 4.1 inches.
7. A 95% confidence interval for µ is
A) (58.16, 74.24).
B) (59.46, 72.94).
C) (65.8, 66.6).
D) (65.86, 66.54).
8. I compute a 95% confidence interval for µ. Suppose I had measured the heights of a random sample of
100 sophomore males rather than 400. Which of the following statements is true?
A) The margin of error for our 95% confidence interval would increase.
B) The margin of error for our 95% confidence interval would decrease.
C) The margin of error for our 95% confidence interval would stay the same, since the level of
confidence has not changed.
D) σ would decrease.
9. The heights of young American women, in inches, are normally distributed with mean µ and standard
deviation σ = 2.4. If I want the margin of error for a 99% confidence interval to be ± 1 inch, I should
select a simple random sample of size
A) 2.
B) 7.
C) 16.
D) 39.
10. The scores of a certain population on the Wechsler Intelligence Scale for Children (WISC) are thought to
be normally distributed with mean µ and standard deviation σ = 10. A simple random sample of 25
children from this population is taken and each is given the WISC. The mean of the 25 scores is x =
104.32. Based on these data, a 95% confidence interval for µ is
A) 104.32 ± 0.78.
B) 104.32 ± 3.29.
C) 104.32 ± 3.92.
D) 104.32 ± 19.60.
11. Suppose we want a 90% confidence interval for the average amount spent on books by freshmen in their
first year at a major university. The interval is to have a margin of error of $2, and the amount spent
has a normal distribution with a standard deviation σ = $30. The number of observations required is
closest to
A) 25.
B) 30.
C) 609.
D) 865.
12. Other things being equal, the margin of error of a confidence interval increases as
A) the sample size increases.
C) the population standard deviation increases.
B) the confidence level decreases.
D) none of the above.
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Ch 10-12a Review
13. The weights of three adult males are (in pounds) 160, 215, and 195. The standard error of the mean of
these three weights is
A) 190.
B) 27.84.
C) 22.73.
D) 16.07.
14. The heights (in inches) of males in the United States are believed to be normally distributed with mean µ.
The average height of a random sample of 25 American adult males is found to be x = 69.72 inches and
the standard deviation of the 25 heights is found to be s = 4.15. The standard error of x is
A) 0.17.
B) 0.69.
C) 0.83.
D) 2.04.
15. Scores on the Math SAT (SAT-M) are believed to be normally distributed with mean µ. The scores of a
random sample of three students who recently took the exam are 550, 620, and 480. A 95% confidence
interval for µ based on these data is
A) 550.00 ± 173.88.
B) 550.00 ± 142.00.
C) 550.00 ± 128.58.
D) 550.00 ± 105.01.
16. Do students tend to improve their Math SAT (SAT-M) score the second time they take the test? A random
sample of four students who took the test twice received the following scores.
Student
First score
Second score
1
450
440
2
520
600
3
720
720
4
600
630
Assume that the change in SAT-M score (second score – first score) for the population of all students
taking the test twice is normally distributed with mean µ. A 90% confidence interval for µ is
A) 25.0 ± 64.29.
B) 25.0 ± 47.54.
C) 25.0 ± 43.08.
D) 25.0 ± 33.24.
17. To estimate µ, the mean salary of full professors at American colleges and universities, you obtain the
salaries of a random sample of 400 full professors. The sample mean is x = $73220 and the sample
standard deviation is s = $4400. A 99% confidence interval for µ is
A) 73,220 ± 11,440.
B) 73,220 ± 572.
C) 73220 ± 431.
D) 73220 ± 28.6.
18. Which of the following is an example of a matched-pairs design?
A) A teacher compares the pretest and posttest scores of students.
B) A teacher compares the scores of students using a computer-based method of instruction with the
scores of other students using a traditional method of instruction.
C) A teacher compares the scores of students in her class on a standardized test with the national
average score.
D) A teacher calculates the average of scores of students on a pair of tests and wishes to see if this
average is larger than 80%.
Use the following to answer questions 19-21:
A researcher wished to test the effect of the addition of extra calcium to yogurt on the “tastiness” of yogurt. A
collection of 200 adult volunteers was randomly divided into two groups of 100 subjects each. Group 1 tasted yogurt
containing the extra calcium. Group 2 tasted yogurt from the same batch as group 1 but without the added calcium.
Both groups rated the flavor on a scale of 1 to 10, 1 being “very unpleasant” and 10 being “very pleasant.” The
mean rating for group 1 was x1 = 6.5 with a standard deviation s1 = 1.5. The mean rating for group 2 was x2 = 7.0
with a standard deviation s2 = 2.0. Assume the two groups are independent. Let µ1 and µ2 represent the mean ratings
we would observe for the entire population represented by the volunteers if all members of this population tasted,
respectively, the yogurt with and without the added calcium.
19. Referring to the information above, assuming two sample t procedures are safe to use, a 90% confidence
interval for µ1 – µ2 is (use the conservative value for the degrees of freedom)
A) –0.5 ± 0.25.
B) –0.5 ± 0.32.
C) –0.5 ± 0.42.
D) –0.5 ± 0.5.
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Ch 10-12a Review
20. Referring to the information above, which of the following would lead us to believe that the t procedures
were not safe to use here?
A) The sample medians and means for the two groups were slightly different.
B) The distributions of the data were moderately skewed.
C) The data are integers between 1 and 10 and so cannot be normal.
D) Only the most severe departures from normality would lead us to believe the t procedures were not
safe to use.
21. Referring to the information above, if we had used the more accurate software approximation to the
degrees of freedom, we would have used which of the following for the number of degrees of freedom for
the t procedures?
A) 199.
B) 198.
C) 184.
D) 99.
Use the following to answer questions 22-24:
A sports writer wished to see if a football filled with helium travels farther, on average, than a football filled with
air. To test this, the writer used 18 adult male volunteers. These volunteers were randomly divided into two groups
of nine subjects each. Group 1 kicked a football filled with helium to the recommended pressure. Group 2 kicked a
football filled with air to the recommended pressure. The mean yardage for group 1 was x1 = 30 yards with a
standard deviation s1 = 8 yards. The mean yardage for group 2 was
x2 = 26 yards with a standard deviation s2 = 6
yards. Assume the two groups of kicks are independent. Let µ1 and µ2 represent the mean yardage we would observe
for the entire population represented by the volunteers if all members of this population kicked, respectively, a
helium- and an air-filled football.
22. Referring to the information above, assuming two sample t procedures are safe to use, a 99% confidence
interval for µ1 – µ2 is (use the conservative value for the degrees of freedom)
A) 4 ± 4.7 yards.
B) 4 ± 6.2 yards.
C) 4 ± 7.7 yards.
D) 4 ± 11.2 yards.
23. Referring to the information above, to which of the following would it have been most important that the
subjects be blind during the experiment?
A) the identity of the sports writer.
B) the direction in which they were to kick the ball.
C) the method they were to use in kicking the ball.
D) whether the ball they were kicking was filled with helium or air.
24. Referring to the information above, if we had used the more accurate software approximation to the
degrees of freedom, we would have used which of the following for the number of degrees of freedom for
the t procedures?
A) 14.
B) 12.
C) 9.
D) 8.
Use the following to answer questions 25-26:
The college newspaper of a large Midwestern university periodically conducts a survey of students on campus to
determine the attitude on campus concerning issues of interest. Pictures of the students interviewed along with a
quote of their response are printed in the paper. Students are interviewed by a reporter “roaming” the campus who
selects students to interview “haphazardly.” On a particular day the reporter interviews five students and asks them
if they feel there is adequate student parking on campus. Four of the students say no. The proportion p̂ that
respond “no” is thus 0.8.
25. Referring to the information above, the standard error SE of the proportion is
pˆ
A) 0.8.
B) 0.64.
C) 0.18.
D) 0.032.
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Ch 10-12a Review
26. Referring to the information above, which of the following assumptions for inference about a proportion
using a confidence interval are violated in this example?
A) The data are an SRS from the population of interest.
B) The population is at least 10 times as large as the sample.
C) We are interested in inference about a proportion.
D) There appear to be no violations.
27. Eighty rats whose mothers were exposed to high levels of tobacco smoke during pregnancy were put
through a simple maze. The maze required the rats make a choice between going left or going right at the
outset. Sixty of the rats went right when running the maze for the first time. Assume that the 80 rats can
be considered an SRS from the population all rats born to mothers exposed to high levels of tobacco
smoke during pregnancy (note that this assumption may or may not be reasonable, but researchers often
assume lab rats are representative of such larger populations since lab rats are often bred to have very
uniform characteristics). The standard error for the proportion p̂ of those who went right the first time
when running the maze is
A) 0.0023.
B) 0.0484.
C) 0.0548.
D) 0.0559.
Use the following to answer questions 28-29:
A newspaper conducted a statewide survey concerning the 1998 race for state senator. The newspaper took a
random sample (assume it is an SRS) of 1200 registered voters and found that 620 would vote for the Republican
candidate. Let p represent the proportion of registered voters in the state that would vote for the Republican
candidate.
28. Referring to the information above, a 90% confidence interval for p is
A) 0.517 ± 0.014.
B) 0.517 ± 0.024.
C) 0.517 ± 0.028.
D) 0.517 ± 0.249.
29. Referring to the information above, how large a sample n would you need to estimate p with margin of
error 0.01 with 95% confidence? Use the guess p = 0.5 as the value for p.
A) n = 49.
B) n = 1500.
C) n = 4800.
D) n = 9604.
30. An inspector inspects large truckloads of potatoes to determine the proportion p in the shipment with
major defects prior to using the potatoes to make potato chips. She intends to compute a 95% confidence
interval for p. To do so, she selects an SRS of 50 potatoes from the over 2000 potatoes on the truck.
Suppose that only two of the potatoes sampled are found to have major defects. Which of the following
assumptions for inference about a proportion using a confidence interval are violated?
A) The population is at least 10 times as large as the sample.
B) n is so large that both the count of successes n p̂ and the count of failures n(1 – p̂ ) are 10 or more.
C) The population size is too small.
D) There appear to be no violations.
Use the following to answer questions 31-32:
An SRS of size 100 is taken from a population having proportion 0.8 of successes. An independent SRS of size 400
is taken from a population having proportion 0.5 of successes.
31. Referring to the information above, the sampling distribution for the difference in the sample proportions,
p̂1 – p̂2 , has mean
A)
B)
C)
D)
0.3.
the smaller of 0.8 and 0.5.
0.15.
The mean cannot be determined without knowing the sample results.
32. Referring to the information above, the sampling distribution for the difference in the sample proportions,
p̂1 – p̂2 , has standard deviation σ pˆ1 − pˆ 2 equal to
A) 1.3.
B) 0.40.
C) 0.047.
D) 0.002.
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Ch 10-12a Review
33. An SRS of 100 of a certain popular model car in 1993 found that 20 had a certain minor defect in the
brakes. An SRS of 400 of this model car in 1994 found that 50 had the minor defect in the brakes. Let p1
and p2 be the proportion of all cars of this model in 1993 and 1994, respectively, that actually contain the
defect. A 90% confidence interval for p1 – p2 is 0.075 ± 0.071.
Suppose the sample of 1993 cars consisted of only 10 cars, of which two had the minor brake defect.
Suppose also the sample of 1994 cars consisted of only 40 cars, of which five had the minor brake defect.
A 90% confidence interval for p1 – p2 is now
A) the same as that for the original sample of 100 and 400 cars.
B) much narrower than that for the original sample of 100 and 400 cars.
C) the same as 99% for the original sample of 100 and 400 cars.
D) It is unsafe to compute using the normal distribution to approximate the sampling distribution of
p̂1 – p̂2 .
Use the following to answer question 34:
In a large Midwestern university (the class of entering freshmen being on the order of 6000 or more students), an
SRS of 100 entering freshmen in 1993 found that 20 finished in the bottom third of their high school class.
Admission standards at the university were tightened in 1995. In 1997 an SRS of 100 entering freshmen found that
10 finished in the bottom third of their high school class. Let p1 and p2 be the proportion of all entering freshmen in
1993 and 1997, respectively, who graduated in the bottom third of their high school class.
34. Referring to the information above, a 99% confidence interval for p1 – p2 is
A) 0.10 ± .050.
B) 0.10 ± .083.
C) 0.10 ± .098.
D) 0.10 ± .129.
35. A manufacturer receives parts from two suppliers. An SRS of 400 parts from supplier 1 finds 20
defective. An SRS of 100 parts from supplier 2 finds 10 defective. Let p1 and p2 be the proportion of all
parts from suppliers 1 and 2, respectively, that is defective. A 95% confidence interval for p1 – p2 is
A) –.05 ± 0.063.
B) –.05 ± 0.053.
C) –.05 ± 0.032.
D) .05 ± 0.032.
Use the following to answer questions 36-37:
A sociologist is studying the effect of having children within the first three years of marriage on the divorce rate.
From city marriage records she selects a random sample of 400 couples that were married between 1985 and 1990
for the first time, with both members of the couple between the ages of 20 and 25. Of the 400 couples, 220 had at
least one child within the first three years of marriage. Of the couples that had children, 83 were divorced within five
years, while in the couples that didn't have children only 52 were divorced within three years. Suppose p1 is the
proportion of couples married in this time frame that had a child within the first three years and were divorced
within five years and p2 is the proportion of couples married in this time frame that did not have a child within the
first two years and were divorced within five years.
36. Referring to the information above, the estimate of p1 – p2 is
A) 0.0884.
B) 0.3100.
C) 0.3375.
D) 0.3773.
37. Referring to the information above, the sociologist had hypothesized that having children early would
increase the divorce rate. She tested the one-sided alternative and obtained a P-value of 0.0314. The
correct conclusion is that
A) if you want to decrease your chances of getting divorced, it is best to wait several years before
having children.
B) there is evidence of an association between divorce rate and having children early.
C) if you want to decrease your chances of getting divorced, it is best not to marry when you are closer
to 30 years old.
D) it is best not to have children.
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Ch 10-12a Review
Confidence Interval Review
Name:________________
1) Julia enjoys jogging. She has been jogging over a period of several years, during which time her physical
condition has remained constantly good. Usually, she jogs 2 miles per day. The standard deviation of her
times σ =1.80 minutes. During the past year Julia has recorded her times required to run 2 miles. She has a
random sample of 90 of these times. For these 90 times the mean x =15.60 minutes. Let µ be the mean
jogging time for the entire distribution of Julia’s 2-mile running times.
a.
Find a 95% confidence interval for µ. Follow the inference toolbox.
b.
What sample size is required to have a margin of error of at most
± 0.2 minutes?
2) How much does a sleeping bag cost? Let’s say you want a sleeping bag that should keep you warm in
temperatures from 20 to 45°F. A random sample of prices ($) for sleeping bags in this temperature range was taken
from Backpacker Magazine: Gear Guide (Vol. 25, Issue 157, No. 2).
80
90
100
120
75
37
30
23
100
110
105
95
105
60
110
120
95
90
60
70
Find a 90% confidence interval for the mean price µ of all summer sleeping bags. Follow the steps of the inference
toolbox.
3) Suppose that 800 students were selected at random from a student body of 20,000 college students and given
shots to prevent a certain type of flu. All 800 students were exposed to the flu, and 600 of them did not get the flu.
Let p represent the probability that the shot will be successful for any single student selected at random from the
entire population of 20,000. Find a 99% confidence interval for p. Follow the steps of the inference toolbox.
4) For large U.S. companies, what percent of their total income comes from foreign sales? A random sample of
technology companies (IBM, Hewlett-Packard, Intel, and others) gave the following data:
62.8
55.7
47.0
59.6
55.3
41.0
65.1
51.1
53.4
50.8
48.5
44.6
49.4
61.2
39.3
41.8
Another independent random sample of basic consumer product companies (Goodyear, Sarah Lee, H.J. Heinz, and
others) gave the following data:
28.0
30.5
34.2
50.3
11.11
28.8
40.0
44.9
60.1
23.1
21.3
42.8
18.0
36.9
28.0
32.5
40.7
a. Find each sample mean, sample standard deviation, and sample size.
b. Find a 90% confidence interval for µ1-µ2 when µ1 represents the technology companies and µ2
represents the consumer companies. Follow the inference toolbox.
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Ch 10-12a Review
5) The U.S. department of Commerce Environmental Data Service gave the following information about average
temperature (°F) in January in Phoenix, Arizona, for the past 39 years. Assume σ = 3.04 °F.
52.8
52.2
52.7
53.8
54.5
48.5
53.3
52.4
51.7
43.2
51.4
42.8
48.5
52.3
51.6
43.7
49.7
49.9
52.6
51.2
50.7
54.2
48.7
56.0
54.0
51.9
50.4
50.7
54.0
52.4
51.5
48.4
46.7
53.0
51.4
49.6
54.6
52.3
54.9
Find a 99% confidence interval for the January mean temperature in Phoenix. Follow the inference toolbox.
6) Suppose an archaeologist discovers only 7 fossil skeletons from a previously unknown species of miniature horse.
Reconstructions of the skeletons of these 7 miniature horses show the shoulder heights (in cm) to be:
45.3
47.1
44.2
46.8
46.5
45.5
47.6
Even though one condition is violated, find a 99% confidence interval for µ, the mean shoulder height of the entire
population of such a horse. Follow the inference toolbox. In your work mention the condition that is violated and
state why you can still carry on with the procedure.
7) David E. Brown is an expert in wildlife conservation. In his book The Wolf in Southwest: The Making of an
Endangered Species (University of Arizona Press), he records the following weights of adult gray wolves from two
regions in Old Mexico.
Chihuahua region: (in pounds) sample 1
86
75
91
70
79
80
68
71
74
64
Durango region: (in pounds) sample 2
68
72
79
68
77
89
62
55
68
68
59
63
66
58
54
71
59
67
Find an 85% confidence interval for the mean differences in weight between the two regions. Follow the inference
toolbox.
8) What price to farmers get for their watermelon? In the third week of July, a random sample of 40 farming
regions gave a sample mean of $6.88 per 100 pounds of watermelon. Assume that σ is known to be $1.92 per 100
pounds. ( Reference: Agricultural Statistics, U.S. Department of Agricultural).
a. Find a 90% confidence interval for the population mean price (per 100 pounds) that farmers in this
region get for their watermelon crop. Follow the inference toolbox.
b. Assume a confidence interval for the watermelon data was calculated and found to be (6.285 to 7.475).
What is the confidence level for this interval?
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Ch 10-12a Review
9) Most married couples have two or three personality preferences in common. Myers used a random sample of
375 married couples and found that 132 had three preferences in common. Another sample of 571 couples found
that 217 had two personality preferences in common. Let p1 be the population proportion of all married couples
with three personality preferences in common and let p2 be the population proportion of all married couples with
two personality preferences in common. Find a 90% confidence interval for p1-p2. Follow the steps of the
inference toolbox.
10) The home run percentage is the number of home runs per 100 times at bat. A random sample of 43 professional
baseball players gave the following data for home run percentages. (Reference: The Baseball Encyclopedia,
Macmillan). The x =2.29 and s =1.40.
a. Compute a 95% confidence interval for the population mean µ of home run percentages for all
professional baseball players. Follow the steps of the inference toolbox.
b. Assume another sample was taken with the same standard deviation. With this new sample a margin
of error of ± .3 was calculated with a 95% confidence level, how large was the sample size?
11) The manager of the dairy section of a large supermarket took a random sample of 250 egg cartons and found
that 40 cartons had at least one broken egg.
a. Find a 90% confidence interval for p. Follow the steps of the inference toolbox.
b. Assume the manger repeated this same process a different week and found the same sample proportion
of cartons broken for 250 egg cartons. Since the manager knows some statistics he calculated a confidence
interval for the mean proportion and found it to be (.11456 to .20544). A couple days later he looked at his
work and realized he forgot to write down the confidence level for his interval. Find the manager’s
confidence level for this interval.
12) Independent random samples of professional football and basketball players gave the following information
regarding their heights (Reference: Sports Encyclopedia of Pro Football and Official NBA Basketball
Encyclopedia).
Football: n = 45,
Basketball: n=40,
x1 = 6.179 feet and s1 = 0.366 feet
x2 = 6.453 feet and s2 = 0.314 feet
Follow the steps of the inference toolbox to construct a 95% confidence interval for the difference between the mean
heights of football and basketball players.
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Ch 10-12a Review
13) At a community hospital, the burn center is experimenting with a new plasma compress treatment. A random
sample of n1=316 patients with minor burns received the plasma compress treatment. Of these patients, it was
found that 259 had no visible scars after treatment. Another random sample of n2=419 patients with minor burns
received no plasma compress treatment. For this group, it was found that 94 had no visible scars after treatment.
Let p1 be the population proportion of all patients with minor burns receiving the plasma compress treatment that
have no visible scars. Let p2 be the population proportion of all patients with minor burns not receiving the plasma
compress treatment who have no visible scars.
Find a 95% confidence interval for p1-p2. Follow the steps of the inference toolbox.
14) Attending sporting events is a popular source of entertainment. When 1000 people were surveyed, 590 said that
getting together with friends was an important reason for attending a sporting event (USA Today).
a. Find a 99% confidence interval for p. Follow the steps of the inference toolbox.
b. Assume we have the same sample proportion as stated above but an unknown sample size. If we want
to be 99% confident and want the margin of error to be ± .06, how large of a sample is needed?
15) From public records, individuals were identified as having been charged with drunken driving not less than 6
months or more than 12 months from the starting date of a given study. Two random samples from this group were
studied. In the first sample of 30 individuals, the respondents were asked in face-to-face interviews if they had
been charged with drunken driving in the last 12 months. Of these 30 people, 16 answered the question accurately.
The second random sample consisted of 46 people who had been charged with drunken driving. During a
telephone interview, 25 of these responded accurately. Assume the samples are representative of all the people
recently charged with drunken driving. Let p1 be the population proportion of those interview face-to-face that
answered correctly and let p2 be the population proportion of those interview over the phone that answered correctly.
Find a 98% confidence interval for p1-p2. Follow the steps of the inference toolbox.
Multiple Choice Answer Key
1. c
11. c
2. d
12. c
3. b
13. d
4. c
14. c
5. b
15. a
6. b
16. b
7. c
17. b
8. a
18. a
9. d
19. c
10. c
20. d
21.
22.
23.
24.
25.
26.
27.
28.
29.
30.
c
d
d
a
c
a
b
b
d
b
31.
32.
33.
34.
35.
36.
37.
a
c
d
d
a
a
b
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