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Unformatted text preview: Chapter 23 Inferences about Means (Review) Name MULTIPLE CHOICE. Choose the one alternative that best carnpletes the statement or answers the question. Using the twtables, software, or a calculator, estimate the critical value of t for the given confidence intervai and degrees
of freedom. ' 1) 80% conﬁdence interval with df m 11 1)
A) 1.280 8) 1.363 C) 2.718 D) 1.356 E) 1.372 2) 95% conﬁdence interval with (if m 15 2)
A) 2.131 B) 1.960 C) 2.120 D) 1.753 E) 2.145 3) 99% conﬁdence interval with df = 24 3)
A) 2.779 B) 2.797 C) 2.492 D) 1.711 E) 2.807 Use the ttables, software, or a calculator to estimate the indicated I’uvalue. 4) P—value for t a 1.76 with 24 degrees of freedom 4)
A) 0.0912 B) 0.0456 C) 0.0592 D) 0.9544 8) 0.0228 5) P~value for M > 1.76 with 24 degrees of freedom 5)
A) 0.1562 B) 0.0781 C) 0.0456 D) 0.9544 E) 0.0911 6) Pwvalue for t s 1.44 with 45 degrees of freedom 6)
A) 0.8914 B) 0.9215 C) 0.1569 D) 0.0785 E) 0.8431 Interpret the conﬁdence interval. 7) Analysis of a random sample of 250 Illinois nurses produced a 95% confidence interval for the 7)
mean annual salary of $42,803 < 0(Nurse Salary) < $49,692. A) We are 95% conﬁdent that the average nurse salary in the US. is between $42,803, and
$49,692.  B) If we took many random samples of Illinois nurses, about 95% of them would produce this
conﬁdence interval. C) We are 95% conﬁdent that the interval from $42,803 to $49,692 contains the true mean salary
of all Illinois nurses. D) About 95% of the nurses surveyed earn between $42,803 and $49,692.
E) About 95% of Illinois nurses earn between $42,803 and $49,692. 8) A credit union took a random sample of 40 accounts and obtained the following 90% conﬁdence 8)
interval for the mean checking account balance at the institution: $2199 < u(baiance) < $3820. A) We are 90% confident that the mean checking account balance in the US is between $2199
and $3820. B) We are 90% sure that the mean balance for checking accounts in the sample was between
$2199 and $3820. C) About 9 out of 10 people have a checking account balance between $2199 and $3820. D) If we took random samples of checking accounts at this credit union, about nine out of ten 0]
them would produce this conﬁdence interval. B) We are 90% cenﬁdent that the mean checking account balance at this credit union is between
$2199 and $3820, based on this sample. 9) You want to estimate the average gas price in your city for a gallon of regular gas. From your 9)
sample of 15 gas stations, you calculate a 95% conﬁdence interval of ($1.98, $2.16) A) You are 95% sure that the average price for a gallon of gas in your city is between $1.98 and
$2.16. B) 95% of all samples of gas stations will have average costs between $1.98 and $2.16. C) You are 95% conﬁdent that the average price for a gallon of gas in the country is within $0.09
of $2.07. D) You are 95% sure that gas stations in this sample have average costs between $1.98 and $2.16. ‘5) If you took many samples of gas stations in your city, about 95% of them would produce this
conﬁdence interval. 10) How many unpopped kernels are left when you pop a bag of microwave popcorn? Quality control 10)
personnel at Yummy Popcorn take a random sample of 50 bags of popcorn. They pop each bag in a
microwave and then count the number of unpopped kernels. The following interval is produced: twinterval for u : with 99% Conﬁdence,
11 < p.(unpopped) < 25 A) About 99% of the sampled bags had between 11 and 25 unpopped kernels. B) We are 99% sure that the average number of unpopped kernels in bags of Yummy brand
popcorn is between 11 and 25 kernels. C) 99% of all samples of Yummy popcorn will produce this confidence interval. D) We are 99% confident that the average number of unpopped kernels in microwave popcorn
bags is between 11 and 25. E) The average number of unpopped kernels in a bag of Yummy popcorn is between 11 and 25
kernels. 11) How tall is your average statistics classmate? To determine this, you measure the height of a 11) random sample of 9 of your 100 fellow students, calculating the following conﬁdence interval:
t—lnterval for p: with 95.00% Conﬁdence,
64.88 < aneight) < 71.12 A) We're 95% sure that the average height of your statistics ciassmates is between 64.88 and 71.12
inches. 8) The average height of your classmates is between 64.88 and 71.1.2 inches. C) 95 of your 100 classmates are between 64.88 and 71.12 inches tall. D) We can be 95% sure that statistics students are between 64.88 and 71.12 inches tall.
E) There's a 95% chance of a classmate being between 64.88 and 71.12 inches tall. i’rovide an appropriate response. 12) You want to determine if the average gas price in your city has exceeded $2.15 per gallon for 12)
regular gas. You take a random sample of prices from 8 gas stations , recording the following prices: $2.13, $2.10, $1.80, $2.09, $2.17, $2.12, $2.10, $2.11. Have the conditions and assumptions for
inference been met? A) No, the nearly normal condition is not met. B) Yes, all conditions and assumptions have been met.
C) No, the sample is not random. D) No, the sample is not representative. E) No, the sample is more than 10% of the population. 13) How tail is your average statistics classmate? To determine this, you measure the height of a 13)
random sample of 15 of your 100 fellow students, finding a mean height of 68 inches and a
standard deviation of 2.3 inches. Have the conditions and assumptions for inference been met? A) No, the sample wasn‘t random.
B) No, the population is not likely to be Normal.
3 C) No, the sample is not representative.
D) Yes, all conditions and assumptions have been met. E) No, the sample is more than 10% of the population. 14) How many unpopped kernels are left when you pop a bag of microwave popcorn? Each day, 14)
quaiity control personnei take a random sample of 50 bags of popcorn. They pop each bag in a
microwave and then count the number of unpopped kernels. Have the conditions and assumptions
for inference been met? A) No, the sample is more than 10% of the population size. B) No, the sample does not meet the Nearly Normal condition.
C) Yes, all conditions and assumption are met. D) No, the sample is not likely to be representative. E) No, this is not a representative sample since the quality control personnel work for the
company and are biased. SHORT ANSWER. Write the word or phrase that best completes each statement or answers the question. 15) Students investigating the packaging of chocoiate chip cookies purchased 10 16——ounce 15)
bags of a particular brand. They carefully weighed the contents of each bag, recording the
I fottowing weights (in ounces): 16.6, 15.2, 16.5, 15.9, 15.9, 16.2, 16.3, 15.8, 15.6, 16.0. The
students plan to test the hypothesis that the mean weight agrees with the company's stated
Weight on each bag. Decide whether or not the conditions and assumptions for inference
with a t—test are satisﬁed. Explain your answer. MULTIPLE CBOICE. Choose the one alternative that best completes the stateuient or answers the question. Use the given sample data to construct the indicated confidence interval for the population mean. 16) n a 10, 32m 137, s z 4.4 16)
Find a 95% confidence interval for the mean. A) (1060,1680)
B) (1057,1683)
C) (11.15, 16.25)
D) (1065,1685)
E) (1060.16.83) 17) n z 30, 326 92.4, s a 7.4 17)
Find a 90% confidence interval for the mean. A) (89.64, 95.16)
B) (90.12, 94.68)
C) (88.68, 96.12)
33) (88.68, 94.68)
E) (90.10, 94.70) 18) Thirty randomiy selected students took the caiculus final. If the sample mean was 82 and the 18)
standard deviation was 6.0, construct a 99% confidence interval for the mean score of all students. A) (78.99, 85.01)
B) (78.98, 86.02)
C) (80.14, 83.86)
D) (80.14, 86.01)
E) (79.30, 84.70) 19) A savings and loan association needs information concerning the checking account balances of its
local customers. A random sample of 111 accounts was checked and yielded a mean balance of
$664.14 and a standard deviation of $297.29. Find a 98% conﬁdence interval for the true mean
checking account balance for local customers. A) ($493.71, $834.57)
B) ($492.52, $835.76)
C) ($488.66, $872.63)
D) ($453.56, $874.72)
E) ($6155.65, $835.76) 20) Among a sample of 75 students selected at random from one college, the mean number of siblings
is 1.4 with a standard deviation of1.2. Find a 95% confidence interval for the mean number of
siblings for all students at this college. A) (1.26.154)
B) (126,143)
C) (72.97, 77.03) 'D) (1.12, 1.68)
11) (137,143) Use the given sample data to construct the indicated confidence intervai for the population mean. 21) The principal randomly selected six students to take an aptitude test. Their scores were:
75.2 87.7 70.5 77.1 82.1 72.9
Determine a 90% confidence interval for the mean score for all students. A) (82.80, 82.80)
B) (72.37, 82.80)
C) (82.80, 72.37)
D) (82.90, 72.27)
E) (72.27, 82.90) 22) The football coach randomly selected ten players and timed how long each player took to perform
a certain drill. The times (in minutes) were:
6.9 8.2 7.0 11.6 7.0 6.2 10.6 10.7 8.9 13.8
Determine a 95% confidence interval for the mean time for all players. 1 A) (10.88, 7.30)
B) (10.78, 7.40)
C) (7.40, 10.88)
D) (73010.88)
E) (74010.78) 19) 20) 21) 22) 23) A random sample of 30 iong distance runners aged 2025 was selected from a running club. The 23)
resting heart rates (in beats per minute) of the runners are shown beiow. Estimate the mean resting
heart rate for the population of long distance runners aged 2025. Give the 95% conﬁdence
interval. 62 ’70 61 64 '75 54 72 68 '74 54
75 70 62 66 '79 73 81 60 66 76
6'7 62 66 69 ‘70 86 76 60 53 ‘71 A) (64.0, 72.2) B) (62.9, 72.2) C) (64.1, 70.1) D) (62.9, 73.0) s) (65.0, 71.1) Determine the margin of error in estimating the yopulation parameter. 2%) Based on a sample of 31 randomly selected years, a 90% conﬁdence interval for the mean annual 24)
precipitation in one city is from 47.7 inches to 50.3 inches. A) 2.6 inches
B) 0.10 inches
C) 1.3 inches
D) 0.38 inches E) Not enough information is given. 25) How tail is your average statistics classmate? To determine this, you measure the height of a 25) random sample of 15 of your 100 feiiow students, ﬁnding a 95% conﬁdence interval for the mean
height of 67.25 to 69.75 inches. A) 1.5 inches B) 1.06 inches
C) 1.25 inches
D) 0.25 inches E) Not enough information is given. 26) How much fat do reduced fat cookies typicaiiy have? You take a random sample of 51 reduced—fat 26) cookies and test them in a lab, constructing the following conﬁdence interval:
t—Intervai for n: with 90.00% Confidence,
2.3 < y(grarns of fat) < 3.4 A) 0.55 grams of fat
B) 1.10 grams of fat
C) 2.85 grams of fat
D) 1.48 grams of fat E) Not enough information is given. 27) A scientist in Smallville tested the cholesterol of a random sample of 35 town residents. He constructed the following conﬁdence interval:
t—interval for p: with 99.00% Confidence,
188 < u(Cholesterol) < 2.06 A) 1.09
s) 197
C) 18
o) 9 E) Not enough information is given. Classify the hypothesis test as lowermtailed, uppermtailed, or two—sided. 28) in the past, the mean running time for a certain type of ﬂashlight battery has been 8.4 hours. The
manufacturer has introduced a change in the production method and wants to perform a
hypothesis test to determine whether the mean manning time has changed as a result. A) Uppermtailed B) Lowerwtailed C) Two4sided 29) At one school, the average amount of time that tenth” graders spend watching television each week
is 21.6 hours. The principal introduces a campaign to encourage the students to watch less
television. One year later, the principal wants to perform a hypothesis test to determine whether the average amount of time spent watching television per week has decreased from the previous
mean of 21.6 hours. A) Two—sided B) Lower—taiied C) Upperwtailed 30) In 1990, the average duration of longdistance telephone calls originating in one town was
7.2 minutes. A long—distance teiephone company wants to perform a hypothesis test to determine whether the average duration of tongdistance phone cails has changed from the 1990 mean of
7.2 minutes. A) Lower—tailed B) Two—sided C) Uppermtailed 31) The manufacturer of a refrigerator system produces refrigerators that are Supposed to maintain a
true mean temperature, u, of 40°F, ideal for certain beverages. The owner of a beverage company does not agree with the refrigerator manufacturer, and will conduct a hypothesis test to determine
Whether the true mean temperature differs from this value. A) Lower—tailed B) Upperwtailed C) Twowsided 27) 28) 29) 30) 31) For the given hypothesis test, explain the meaning of a Type I error or a Type II error, as specified. 32) In the past, the mean running time for a certain type of flashlight battery has been 9.2 hours. The 32)
manufacturer has introduced a change in the production method and wants to perform a hypothesis test to determine whether the mean running time has increased as a result. The
hypotheses are: H 0 : u m 9.2 hours
H A : u > 9.2 hours
Explain the result of a Type 1 error. A) The manufacturer will decide the mean battery life is 9.2 hours when in fact it is greater than
9.2 hours. B) The manufacturer will decide the mean battery life is greater than 9.2 hours when in fact it is
9.2 hours. C) The manufacturer wili decide the mean battery life is greater than 9.2 hours when in fact it is
greater than 9.2 hours. ' D) The manufacturer wiii decide the mean battery life is greater than 9.2 hours when in fact it is
less than 9.2 hours. B) The manufacturer will decide the mean battery life is less than 9.2 hours when in fact it is
greater than 9.2 hours. 33) A manufacturer claims that the mean amount of juice in its 16—ounce bottles is 16.1 ounces. A 33) consumer advocacy group wants to perform a hypothesis test to determine whether the mean
amount is actually less than this. The hypotheses are: H0 : u: 16.1 ounces
H A : u < 16.1 ounces
Explain the result of a Type I error. A) The advocacy group will conclude that the mean amount of juice is less than 16.1 ounces
when in fact it is less than 16.1 ounces. B) The advocacy group wili conclude that the mean amount of juice is less than 16.1 ounces
when in fact it is 16.1 ounces. C) The advocacy grOup will conclude that the mean amount of juice is greater than 16.1 ounces
When in fact it is 16.1 ounces. D) The advocacy group will conclude that the mean amOunt of juice is 16.1 ounces when in fact it
is iess than 16.1 ounces. 5) The advocacy group will conciude that the mean amount of juice is 16.1 ounces when in fact it
is 16.1 ounces. 34) in 1990, the average math SAT score for students at one school was 4777. Five years later, a teacher 34)
wants to perform a hypothesis test to determine whether the average SAT score of students at the
school has changed from the 1990 mean of 477. The hypotheses are:
H G : u = 477
H A : pi := 477
Explain the result of a Type II error. A) The teacher will conclude that the mean math SAT score at the school is different when in fact
it is the same. B) The teacher will conclude that the mean math SAT score at the school has increased when in
fact it is the same. C) The teacher will conclude that the mean math SAT score at the schooi has decreased when in
fact it is the same. D) The teacher will conclude that the mean math SAT score at the school is the same when in fact
it is different. E) The teacher will conclude that the mean math SAT score at the school is the same when in fact
it is the same. 35) A man is on trial accused of murder in the first degree. The prosecutor presents evidence that he 35)
hopes will convince the jury to reject the hypothesis that the man is innocent. This situation can be
modeled as a hypothesis test with the following hypotheses: H 0 : The defendant is not guilty. H A : The defendant is guilty.
Explain the result of a Type II error.
A) The jury will conclude that the defendant is guilty when in fact he is not guilty.
B) The jury will conclude that the defendant is guilty when in fact he is guilty.
C) The jury will conclude that the defendant is not guilty when in fact he is not guilty.
D) The jury will conclude that the defendant is not guilty when in fact he is guilty. E) The jury will fail to reach a decision. Use a hypothesis test to test the given claim. 36) Is the mean weight of female college students still 132 pounds? To test this, you take a random 36)
sample of 20 students, finding a mean of 137 pounds with a standard deviation of 14.2 pounds. Use
a signiﬁcance level of 0.1. A) Fail to reject the null. hypothesis of u2132. with a P—vaiue of O.8682.There is not sufﬁcient
evidence that the weight of female students has changed. B) There is not enough information to perform the test. C) Fail to reject the null hypothesis of u=132 with a P—vaiue of 0.9341.T'here is not sufﬁcient
evidence that the weight of female students has changed. D) Reject the null hypothesis of nmIBZ with a Pwvalue of 0.0659. There is sufﬁcient evidence that
the weight of female students has changed. E) Fail to reject the null hypothesis of u=132 with a P—value of 0.1318. There is not sufﬁcient
evidence that the weight of female students has changed. 37) Marc wants to know if the mean age of the prison population in his city is less than 26 years. He 37)
obtains a random sample of 25 prisoners, and finds a mean age of 24.4 years and a standard
deviation of 9.2 years. At a significance level of 0.05, what is his conclusion? A) Fail to reject the null hypothesis of u 2 26 with a P—value of 0.8034. There is not sufﬁcient
evidence that the mean age is less than 26 years. B) Reject the null hypothesis of p. a 26 with a Pwvalue of 0.0425. The evidence suggests that the
mean age is iess than 26 years. C) There is not enough information to perform the test. D) Reject the null hypothesis of p. = 26 with a P—value of 0.018. There is sufﬁcient evidence that
the mean age is less than 26 years. E) Fail to reject the nuli hypothesis of it u 26 with a P—value of 0.1966. There is not sufficient
evidence that the mean age is less than 26 years. 38) A iarge software company gives job applicants a test of programming ability, and the mean score 38)
for the test has been 160 in the past. Twenty—five apphcants are randomiy selected from one large
university and they produce a mean score of 165, with a standard deviation of 13. At a significance level of 0.05, does this indicate that the sample comes from a population with a mean score greater
than 160? A) Yes. With a P—value of 0.0024, we reject the null hypothesis of uzi60.
B) Yes. With a P—value of 0.0332, we reject the null hypothesis of uzi60.
C) No. With a P—value of 0.9668, we fail to reject the nuil hypothesis of um160.
D) No. With a P—vaiue of 0.9336, we fail to reject the null hypothesis of [um—W160.
E) No. With a P—vaiue of 0.0664, we fail to reject the null hypothesis of [M160 Previde an appropriate response. 39) A hypothesis test for a population mean is to be performed. True or false: for a fixed sample size, 39)
increasing the signiﬁcance level will decrease the power of the test?
A) True B) Faise
40) A hypothesis test for a population mean is to be performed. If the significance Ievei is fixed, how 40) wili increasing the sample size affect the power of the test?
A) The power wiii not change.
B) The power wiii increase. C) The power wiil decrease. 41) Suppose you have obtained a conﬁdence interval for ti, but wish to obtain a greater degree of 41)
precision. Which of the foilowing would result in a narrower confidence interval? A. increasing the sample size whiie keeping the conﬁdence level ﬁxed
B. Decreasing the sample size while keeping the confidence level fixed
C. Increasing the conﬁdence level while keeping the sample size fixed
D. Decreasing the cenﬁdence level while keeping the sample size fixed A)BandD B)BandC C)CandD D)AandC E)Aar1dD 10 SHORT ANSWER. Write the word or phrase that best completes each statement or anSWers the question. 42) A manufacturer claims that the mean weight of flour in its 32*ounce bags is 32.1. ounces. A 42)
ttest is performed to determine whether the mean weight is actually less than this. The
hypotheses are HO 2}: x 32.1 ounces H A : p. < 32.1 ounces. The mean weight for a sample of 45 bags of flOur was 30.7 ounces. Suppose that the
P~value corresponding to this sample data is 0.001. Give an interpretation of the P~value.
Would you feel conﬁdent in concluding that the mean weight is less than 32.1 ounces? 43) Based on a sample of size 25, a researcher obtains an estimate of 64.4 inches for the mean 43)
height of all women aged 30—40. At the 95% conﬁdence level, the margin of error is
1.2 inches. Do you agree with the interpretation below? If not, explain Why not and give a
correct interpretation. Researchers interpretation: “We can be 95% confident that the height of a randomly
selected woman will differ from 64.4 inches by at most 1.2 inches." MULTIPLE CHOICE. Choose the one alternative that best completes the statement or answers the question. 44) Which of the following is true about Student‘s t—models? 44)
I. They are unimodal, symmetric, and bell—shaped.
II. They have fatter tails than the Normal model.
III. As the degrees of freedom increase, the t—models look more and more like the Normal. A) I, II, III B) I and III C) I only D) Il an III E) I and II 45) A professor was curious about her students' grade point averages (GPAs). She took a random 45)
sample of 15 students and found a mean GPA of 3.01 with a standard deviation of 0.534. Which of
the following formulas gives a 99% confidence interval for the mean GPA of the professor's
students? A) 3.01 a: 2.977(0534/Jii)
B) 3.01 a 2.977(0.534/«/i5)
C) 3.01 e 2.947(0534/«f1—5)
D) 3.01 e 2.567(0.534NIE)
E) 3.01 a 2.947(0.534/«/il) SHORT ANSWER. Write the word or phrase that best completes each statement or answers the question. 46) The distribution of the number of vacation days per year offered by different US. 46)
companies is skewed to the right. The mean and standard deviation of the 60 companies in
our sample were 22 days and 9 days, respectively. Specify the sampling model (shape,
center, spread) for the mean number of vacatiori days of such samples. 11 MULTEPLE CHOiCE. Choose the one alternative that best completes the statement or answers the question. 47) ‘Nhich statement correctly compares t—distributions to the normal distribution? 47)
l. t distributions are also mound shaped and symmetric.
II. t distributions have less spread than the normal distribution.
lII. As degrees of freedom increase, the variance oft distributions becomes smaller. A) l and ll only
13) ll only C) I only D) I, II, and III
E) land Ill only 48) A random sample of 120 classrooms at a large university found that 70% of them had been cleaned 48)
properly. What is the standard error of the sample proportion? A) 0.046 13) 0.028 C) 0.458 D) 0.082 E) 0.042 49) An elementary school principal wants to know the mean number of children in families whose 49)
children attend this school. He checks all the families using the school’s registration records, and we
use the TI—83 to create a 95% conﬁdence interval based on a twdistribution. This procedure was not
‘ appropriate. Why? A) At a given school families are not randomly selected. B) Since these families are from only one school, the family sizes may be skewed. C) The population standard deviation is known, so he should have used a z—model.
D) The entire population of families was gathered so there is no reason to do inference. E) The recent record—setting family with twelve children is probably an outlier. SHORT ANSWER. Write the word or phrase that best completes each statement or answers the question. 50) A government report on housing costs says that single—family home prices nationwide are 50)
skewed to the right, with a mean of $235,700. We collect price data from a random sample
of 50 homes in Orange County, California. The standard deviation of the 50 homes in our
sample was $25,500. Specify the sampling model (shape, center, spread) for the mean price
of such samples. 51) A government report on housing costs says that single—family home prices nationwide are 51)
skewed to the right, with a mean of $235,700. We collect price data from a random sample
of 50 homes in Orange County, California. Suppose we hope improve our estimate by
choosing a new sample. How many home prices must we survey to have 90% confidence
of estimating the mean local price to within $2000? 12 MULTIPLE CHOICE. Choose the one alternative that best completes the statement or answers the question. 52) A company checking the productivity of its assembly line monitored a random sample of workers
for severai days. They found that a 95% confidence interval for the mean number of items
produced daily by each worker was (23, 27). Which is true? A) 95% of the workers sampled produced between 23 and 3'7 items a day. B) 95% of all the workers average between 23 and 27 items a day. C) Workers produce an average of 23 to 27 items on 95% of the days. D) We‘re 95% sure that the mean daily worker output is between 23 and 27 items. E) 95% of samples would show mean production between 23 and 27 items a day. 53) A wildlife biologist wants to determine the mean weight of adult red squirrels. She captures 10
squirrels she believes to be representative of the species and weighs them, ﬁnding a mean of 12.32
grams and standard deviation of 1.88grn. Assuming these squirrels can he considereda random
sample of all red squirrels which of the following formulas gives a 95% confidence interval for the
mean weight of all squirrels? A) 12.32 a 2.26 34:35?» 41—6 B) 12.32 a 2.22 3483 «1%
1.88
a] D) 12.32 i 2.262 3483? «[53 E) 12.32 i 2.22 3E;— 45 (1)1232 a 1.9 SHORT ANSWER. Write the word or phrase that best completes each statement or answers the question. 54) A government report on standard of living says that family incomes nationwide are 54)
skewed to the right, with a mean of $33400. We collect income data from a random sample
01350 local families. Why is it okay to use these data for inference even though the
population is skewed? 55) A government report on standard of living says that family incomes nationwide are 55)
skewed to the right, with a mean of $33400. We collect income data from a random sample
of 50 locai families. This sample of randomly chosen families produced a 90% conﬁdence
interval for the local mean family income of (32882, 44761). Does this interval provide
evidence that family incomes are unusually high here? Explain briefly. 13 52) 53) MULTIPLE CHOICE. Choose the one alternative that best completes the statement or answers the question. 56) Food inspectors need to estimate the level of contaminants in food products packaged at a certair 56)
factory. Initial tests were based on a small sample but now the inspectors double the sample size for
a followuup test. The main purpose of the larger sample is to A) reduce new response bias. 8) decrease the standard deviation of the sampling model.
C) reduce response bias. {3) decrease the variability in the population. E) reduce confounding due to other variables. 14 Answer Key ‘ ‘
Testname: CHAPTER 23 INFERENCES ABOUT MEANS (REVIEW) 1) B
2) A
3) B
4) B
5) E
6) B
’7) C
8) E
9) A
10) B
11) A
12) A
13) E
14) C
15) The data probably comprise a random sample, although, if the bags were all purchased together, they were probably
packaged at the same plant. The sample comprises less than 10% of all the bags of the particular brand of cookies. The
nearly normal condition seems reasonable since the histogram is unimodal and fairly symmetric with no apparent
outliers.
16) D
17) E
18) B
19) D
20) D
21) B
22) D
23) E
24) C
25) C
26) A
27) D
28) C
29) B
30) B
31) C
32) B
33) B
34) D
35) D
36) E
37) E
38) B
39) B
40) B
41) E
42) If the null hypothesis were true (i.e., if the mean weight really were 32.1 ounces), the probability of observing a sample
mean as small or smaller than 30.7 ounces would be 0.001. Since the Pwvalue is so small, the evidence against the null
hypothesis is overwhelming. 15 Answer Key
Testname: CHAPTER 23 INFERENCES ABOUT MEANS (REVIEW) 43) The researcher‘s interpretation is not correct since the margin of error refers to the difference between the estimate and
the true mean, not to the difference between the estimate and the height of an inciividual woman. The correct interpretation is: We can be 95% conﬁdent that the estimate of 64.4 inches differs from the true mean by at most
1.2 inches. 44) A
45) B 9
46) t5{22, 47) E
48) E
49) D
50) :49(235700, 3606.24.) 25500
4; We need to sample approximately 457 home prices. (Or 440 using za+ = 1.645 )
52) D
53) A
54) Large sample size 55) No; this county's mean could be the same as the national mean because 33400 is in the confidence interval.
56) B *— .—
51) ME = t n_1 x SE(y) or 2000 = (1.676{ ] or J; : 21369 or n = 456.6 16 ...
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 Spring '09
 Mr.Sun

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