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32 Sample Exarnination Two Section E<br />

6. If a 95% confidence interval is given by (86^52, 89.48), which of the <strong>fo</strong>llowing could<br />

be a99o/o confidence interval <strong>fo</strong>r the same data?<br />

L (86.98, 89.42)<br />

II. (86.37,89.63)<br />

III. (87,89)<br />

(A) I only<br />

(B) II only<br />

(C) III only<br />

(D) I and Ill<br />

(E) II and III<br />

7. Which of the <strong>fo</strong>llowing represents a probability density function?<br />

(A) [0.0 <strong>fo</strong>r2


Section I Sample Examination Ttvo 33<br />

8. Maritsa scored 82 on a geometry exam <strong>fo</strong>r which the class mean was 74 and the<br />

standard deviation 3.2 and she scored 86 on a biology exam <strong>fo</strong>r which the class mean<br />

was 77 rvith a standard deviation of 2.9.In comparison to other members of each of<br />

these classes, which of the <strong>fo</strong>llowing conclusions can you draw?<br />

(A) Her per<strong>fo</strong>rmance on the geometry exam was L:etter than her per<strong>fo</strong>rmance c,n the<br />

biology exam.<br />

(B) Her per<strong>fo</strong>rmance on the biology exam was better than her per<strong>fo</strong>rmanee on the<br />

geometry exam.<br />

(C) Her relative per<strong>fo</strong>rrnance was the same <strong>fo</strong>r both exams.<br />

(D) Her relative per<strong>fo</strong>rmance was graded unfairly.<br />

(E) No conclusion can be drawn frorn this data.<br />

[-l<br />

Answer<br />

ll<br />

9. Assurning that birthdays are uni<strong>fo</strong>rmly distributed throughout the week, the probability<br />

that trvo strangers passing each other on the street were both bom on Sulday is<br />

(A) 1t7<br />

(B) 2t7<br />

(c) 1t4e<br />

(D) 2t4e<br />

(E) 4t4e<br />

10. Which of the <strong>fo</strong>llowing are characteristics of a r-distribution curve?<br />

l. The graph of a l-distribution extends infinitely to the left and to the right and<br />

approaches the x-axis asymptotically as x increases in absolute value.<br />

IL There are an infinite number of different /-curves, each determined by a<br />

parameter called degrees of freedom.<br />

Ill. The maximum point on the graph of a r-distribution occurs at its mean which<br />

is always 0.<br />

(A) I only<br />

(B) II only<br />

(C) Iil only<br />

(D) I and III only<br />

(E) I, il, and III<br />

EAnswer<br />

Answer<br />

tt<br />

tl<br />

ot<br />

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34 Sample Examination Two Section E<br />

ll' A teacher raised each student's grade by t0 points on an algebra exam. Which of the<br />

<strong>fo</strong>llowing describes the correlation betu,een students' original srades and their adjusted<br />

grades?<br />

(A) slightly negatrve<br />

(B) slightly positive<br />

(C) close to 0<br />

(D) -1<br />

(E) I<br />

12. In conducting a hypothesis test, thep-rralue is the<br />

(A) probability of obtaining a result as extreme or more extreme than the one<br />

obtained if the null hvpothesis is true<br />

(B) significance level of the test<br />

(C) probability of making a T1,pe I error<br />

(D) probabilitv of making a T,vpe II error<br />

(E) probability that the null h.vpothesis is true<br />

13. In constructing a confidence interval based on a large sample to estimate the mean p<br />

of a population with a knorm standard deviation o, which of the <strong>fo</strong>llon,ing does NOT<br />

affect the rvidth of the confidence interval?<br />

(A) the sample mean<br />

(B) the popuiation standard deviation<br />

(C) the confidence level<br />

(D) the sample size<br />

(E) the sample standard deviation<br />

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Answer<br />

Anslver<br />

Answer


Section tr<br />

14. Which of the <strong>fo</strong>llov-'ing are conditions <strong>fo</strong>r a binomial experirnent'/<br />

Sarnptre Examination Two 35<br />

I. The number of trials n is a fixed number.<br />

II. T'he n trials are independent.<br />

IIi. The probabilifl of success p is equal to the probabilitS' of failure q'<br />

(A) i only<br />

(B) II only<br />

(C) III oniy<br />

(D) I and ll onl,r,<br />

(E) I, II. and III<br />

15. Which of the <strong>fo</strong>llowing is NOT true concerning sampling distributions?<br />

Answer<br />

r--]<br />

ll<br />

(A) If the sample size n is large, the sampling distribution of T, drawn from a normal<br />

population, is approximately normal.<br />

(B) The mean of the sampling distribution of p is equal to the population propor-tion<br />

t)<br />

(C) The mean of the sampling distribution of the difference of trvo means (x, - rr) is<br />

equal to the difference of the population means (l'L'- llr).<br />

(D) The standard deviation of the sampling distribution of I is (r1,6., where o is the<br />

population standard deviation.<br />

(E) The standard deviation of the sampling distribution of the differences of two<br />

means 6x,-z.is equal to the sum of the respective population standard deviations.<br />

Answer<br />

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36 Sarnple Exarnimation Two Section I<br />

16. The all-time leader in career bafting average among major league basebail players is Ty<br />

Cobb with a career average of 0.366. This means he got a hit in 36.5oh of his official<br />

at-bats. What was Cobb's probabiliry of getting at least one hit in <strong>fo</strong>ur official at-bats?<br />

(A) 0.092<br />

(B) 0.134<br />

(c) 0.162<br />

(D) 0.366<br />

(E) 0.838<br />

17. Which of the <strong>fo</strong>lloiving accurately describes the polr,er of a statistical test of<br />

hypothesis?<br />

(A) It is equal to the p-value.<br />

(B) It is equal to 1- (p-value).<br />

(C) It is equal to d, the significance level.<br />

(D) It is the probability that a test using a fixed value of s will reject H,, when a<br />

particular alternative value of the parameter is true.<br />

(E) It is equal to p.<br />

Answer<br />

Answer<br />

I 8. The equation of the least squares regression line lor a set of points in a scatterplot is<br />

given by i = 2.2+ 0.8lx. The point (5, 7) is one poinr on this scatterplot. Which of the<br />

<strong>fo</strong>llowing is the residual <strong>fo</strong>r the point (5,7)?<br />

(A) 0,71<br />

(B) 0.7s<br />

(c) 4.0s<br />

(D) 6.25<br />

(E) 7.87<br />

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Section t Sample Exarnination T\vo 37<br />

19. 'fhe table below shows the probability distribution <strong>fo</strong>r the number of tails (X) in five<br />

tosses of a fair coin. What is E(X)" the exnected value of X?<br />

(A) 2.0<br />

(B) 2.5<br />

(c) 3.0<br />

(D) 3.5<br />

(E) 4.0<br />

X 0 I a J 4 5<br />

D/ta\ 03125 r5525 .3r25 .3t25 15625 .03125<br />

20" Which of the <strong>fo</strong>llowing statemen"ts is a consequence of the Central Limit Theorem?<br />

I. If the original population is uni<strong>fo</strong>rmly disstributed, then the sampling<br />

distribution of x rvill be uni<strong>fo</strong>rnt <strong>fo</strong>r large samples.<br />

II. The sampling distribution of x will be approximately normal <strong>fo</strong>r large samples.<br />

III. The mean of the sampling distribution of t will be close to I <strong>fo</strong>r large samples.<br />

(A) I only<br />

(B) II only<br />

(C) III only<br />

(D) II and III only<br />

(E) I, II, and III<br />

21 " The probability of a tourist visiting an area cave is 0.70 and of a tourist visiting a nearby<br />

park is 0.60. The probability of visiting both places on the same day is 0.40. The<br />

probability that a tourist visits at least one of these two places is<br />

(A) 0.08<br />

(B) 0.28<br />

(c) 0.42<br />

(D) 0.e0<br />

(E) 0.9s<br />

EAnswer<br />

Answer<br />

Ansrver<br />

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38 Samp[e Examination Two Section I<br />

22. The correlation between height and weight among men betr,veen the ages of 18 and 70<br />

in the United States is appro.ximately 0.42. Which of the <strong>fo</strong>lloivine conciusions does<br />

NOT <strong>fo</strong>llow from the data?<br />

(A) Talier men tend to be heavier.<br />

(B) Changing the units of 'weight and height wouid stiil yieid the sarne correiation value.<br />

(C) Heavier mell tend io be tailer.<br />

(D) [f a man in this gloup ciranses his diet and gains ] 0 pounds, he is likeiy to get taller.<br />

(E) There is a moderate association betn'een a il]an's height and weight.<br />

23. A high school guidance counselor wishes to compare the PSAT results <strong>fo</strong>r the male and<br />

female students in the junior ciass at your high school. \\'hich is the best technique <strong>fo</strong>r<br />

gathering the data needed?<br />

(A) census<br />

(B) experiment<br />

(C) observational study<br />

(D) sample survey<br />

(E) a double blind experiment<br />

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Answer<br />

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Answer


Section I Sample Examination Two 39<br />

24. The stem plot below summarizes the number of gold medals earned by 40 countries in<br />

the Winter Olympics <strong>fo</strong>r 1924-1998.<br />

0 827990201 I 1001 101 10001000<br />

l 988<br />

2 9571<br />

3 9895<br />

43<br />

59<br />

6t<br />

78<br />

88<br />

The data depicts a distribution that is<br />

(A) skewed to the left<br />

(B) skerved to the right<br />

(C) symmetric<br />

(D) uni<strong>fo</strong>rm<br />

(E) not determinable from the in<strong>fo</strong>rmation given<br />

Ansrver<br />

25. A tire manufacturer claims that it has developed a new all-season radial tire <strong>fo</strong>r<br />

passenger cars (excluding SUVs) which has a shorter skid distance than the known mean<br />

skid distance, 140 feet, <strong>fo</strong>r all tires currently available. A consumer group wishes to test<br />

this claim. If 1.2 represents the true mean skid distance <strong>fo</strong>r this new tire, which of the<br />

<strong>fo</strong>llowing states the null hypothesis and alternative hypothesis that the consumer group<br />

should test?<br />

(A) H.: p < 140 ft. H,: lt > 140 ft.<br />

(B) H": /1< 140 ft. H^: lt > 140 ft.<br />

(C) H,: lt= I40 ft^ H^: /1< 140 ft.<br />

(D) H": F = 140 ft. H^: P < 140 ft.<br />

(E) H.: F = 140 ft' H^: F + 140 ft.<br />

lAnswer<br />

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4CI SarnpBe Examiuration Two Sectiom !<br />

25. Suppose that A and B are events in a sample space with P(A) = 0.8 and P(Blal = 61.5.<br />

Theri P(AandB) =<br />

(A) 0.3<br />

(B) 0.4<br />

(c) 0.62s<br />

(D) 0.8<br />

(E) i<br />

27 . A telephone survey of 1000 adult Americans ret eals the <strong>fo</strong>llowing data conceming the<br />

President's tax cut plan<br />

Support Oppose Undecided<br />

Male 300 180 90<br />

Female 2ra 190 30<br />

Suppose a study is conducted to test the assoication between gender and position on the<br />

tax cut plan. What is the expected number in the cell representing females who support<br />

the tax cut plan?<br />

(A) 210<br />

(B) 21s<br />

(c) 21e.3<br />

(D) 240.3<br />

(E) Not enough in<strong>fo</strong>rmation given<br />

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Section I Saenple Exarslinat[on Two 43<br />

28. Two independent random samples of size nr= 45andnz= 38. r,vith respective standard<br />

deviations 6r=2.3 and dz= 1.8, are drawn from trvo normally distributed populations.<br />

Which of the <strong>fo</strong>llor,ving represents an estimate of the standard deviation of the sampling<br />

distribution corresponding to xt- x2?<br />

(A) 0.2s<br />

rB) 0.31<br />

(c) 0.4s<br />

(D) 0.s0<br />

(E) 2,05<br />

29. SRS refers to a simple random sample. Suppose an SRS of size n is drawn from a<br />

population. Which of the <strong>fo</strong>llowing accurately character\zes this sample?<br />

I. It is a sample drawn in such a manner so that every set of n subjects in the<br />

population has an equal chance to be the sample chosen.<br />

Il. It is a sample drawn in such a manner so that every subject has some chance<br />

of being chosen.<br />

III. It is a sample drawn in such a manner that every subject in the population has<br />

an equal chance of being selected.<br />

(A) I only<br />

(B) II only<br />

(C) III only<br />

(D) II and III only<br />

(E) I, II, and III<br />

nAnsrver<br />

Answer<br />

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l'l Sample Examinaticn Two Section tr<br />

30. The points (x, y) on a scatterplot <strong>fo</strong>rm an<br />

can be concluded aboul the correlation r<br />

(A) r deueases in absolute value<br />

(B) r increases in absoluie value<br />

(C) r remains constant<br />

(D) the value of r changes sign<br />

(E) nc conclusion can be drarvn<br />

ellipse. As the ellipse becomes thinner. what<br />

between the variabies x and y'i<br />

EAnsrver<br />

31. The histogram below displays a set of measurements. Which of the boxplots belou'<br />

disolavs the same set of measurements?<br />

B<br />

7<br />

6<br />

>.5 O-<br />

C<br />

Oi<br />

l'<br />

o<br />

E3 LL<br />

(A) -il- E<br />

(D)<br />

ffl-.-<br />

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2<br />

1<br />

0<br />

q<br />

(B)<br />

(E)<br />

(c)<br />

o<br />

Answer


Section tr Sample Examination T\vo<br />

32. The correlation r between the magnitude of an earthquake and the depth below the<br />

surface of the earlh at which the quake occurs has been determined experimentally to<br />

be about 0.51, Suppose we use the magnitude of the earthquake (x) to predict the depth<br />

below the surface (y) at which the quake occurs. We can infer that<br />

(A) the least squares regression line ofy on x has slope equal to 0.51<br />

(B) the fraction of the variatioir in depths explained by the least squares regression<br />

line ofy on x is 0.26<br />

(C) about 5lYo of the time, the magnitude of an earthquake will accurately predict<br />

the depth at which the earthquake occurs<br />

(D) the numerical value of the depth is usually 51% of the numerical value of the<br />

earthquake<br />

(E) twenty-six percent of the data values lie on the leas{ squaies regression line<br />

33. A report from the Maine Department of Inland Fisheries and Wildlife indicates that<br />

there occurs on average one fatality per 100 collisions between cars and deer. In 300<br />

collisions between a car and a deer, what is the expected number of fatalities and the<br />

standard deviation?<br />

(A) mean: 0.33 standard deviation : 0.01<br />

(B) mean: 1 standard deviation : 0.01<br />

(C) mean : 3 standard deviation : 1.72<br />

(D) mean: 3 standard deviation :2.97<br />

(E) mean: 30 standard deviation : 3.0<br />

43<br />

TAnswer<br />

Answer<br />

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Sample Examination TWo Section I<br />

34. Johannes Kepler (1571-1630) was able to show that the square of the period of<br />

revolution of a planet is proportional to the eube of its mean distance from the sun. The<br />

equation y = 0.001118x''. where x is the distance of a planet irom the sun (in millions<br />

of miles) and y is the period of revolution (in years) of a planet around the sun, is a<br />

power regression model ivhich represents this relationslrip. Which of tire <strong>fo</strong>iiowing lviii<br />

produce a linear representation of this inodel?<br />

(A) plotting y versers ln x<br />

(B) plotting x versus ln x<br />

(C) plotting x versus ln y<br />

(D) plotting ln x versus ln y<br />

(E) constructing the residuai plot <strong>fo</strong>r the scatterplot of y vs. r<br />

3 5 . Which of the <strong>fo</strong>llowing is an appropriate graph to display univariate categorical data?<br />

(A) stemplot<br />

(B) histogram<br />

(C) boxplot<br />

(D) pie chart<br />

(E) scatterplot<br />

Answer<br />

Ansrver<br />

36. A large university is considering introducing a new major in Economic Geography and<br />

wishes to poll the current student body <strong>fo</strong>r their opinion of the feasibility of introducing<br />

such a rnajor. The Office of Public Relations mails a questionnaire on this issue to a<br />

SRS of 2000 students currently enrolled in the university. Of the 2000 questionnaires<br />

mailed, 532 have been returned of which2lg students supporl the new major. Which<br />

of the <strong>fo</strong>llowing represents the population <strong>fo</strong>r this study?<br />

(A) the 2000 students receiving the questionnaire<br />

(B) the 532 students who responded<br />

(C) the 219 students who support the nerv major<br />

(D) the 2000 students selected represent a sample of the population of all currently<br />

enrolled students<br />

(E) all students who are currently enrolled and all past alumni of the university<br />

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Section I Sample Examination Two<br />

37. A Physicians' Study Group wishes to design a matched pairs test to determine the<br />

effects of a medication on reducing the elevated cholesterol levels in 200 adults in the<br />

35-65 age group. Which of the <strong>fo</strong>llowing represents such a design?<br />

(A) The Physicians'Group compares cholesterol levels of each patient be<strong>fo</strong>re he/she<br />

begins a daily regimen of the medieine to the patient's cholesterol level after six<br />

weeks of using the medication.<br />

(B) The Physicians'Group compares the cholesterol ievels of tire patients using the<br />

medicine <strong>fo</strong>r six weeks with the cholesterol levels of 200 aduits in the same age<br />

group who exhibited elevated cholesterol ievels and did not take the medicine.<br />

(C) The Physicians' Group compared the mean cholesterol level of the 200 patients<br />

six weeks after using the medicine with a published national mean cholesterol<br />

level <strong>fo</strong>r ali adults in this age group.<br />

(D) The Physician's group compares cholesterol levels of the 200 patients using the<br />

medicine <strong>fo</strong>r six weeks with the cholesterol levels of 200 adults in the same ase<br />

group who were taking a placebo.<br />

(E) All of the above are representative of a matched pairs design.<br />

3 8. Let X represent the number of independent rolls of a fair die required to obtain the first<br />

"2".What is P(X = 5)?<br />

(A) (1/6)'(s/6)<br />

(B) (1/6)4<br />

(c) (s/6)'( 1/6)<br />

(D) (s/6)'<br />

(E) (5.6)'<br />

Answer<br />

Answer<br />

45<br />

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Sample Examination Tlvo Section I<br />

39. A local university has a "drop-in center" located near the Student Union rvhere students<br />

can "drop-in" to speak to a counselor on any issue or concern whether personal or<br />

academic. A researcher stations herself at a receptionist's desk during a few random<br />

evenings to collect data on whether men or women are more likely to use this service<br />

and whether a particular class (freshman, sophornore, junior. senior) is more likely to<br />

"drop-in." This study may be described as a<br />

(A) controlled experiment<br />

(B) matched pairs design<br />

(C) census<br />

(D) observational study<br />

(E) a double blind completely randomized experirnent<br />

40. A researcher wishes to use a 95o/o confidence interval to estimate the proportion of<br />

Americans who have visited an entertainment theme park near Orlando rvithin the last<br />

five years. The researcher rvishes to choose a size that will insure a margin of error not<br />

to exceed 0.05. Which of the <strong>fo</strong>llowins is the smallest size that meets these criteria?<br />

(A) 40<br />

(B) 200<br />

(c) 400<br />

(D) 600<br />

(E) 800<br />

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Section II Sample Examination TWo<br />

Section II<br />

Part A<br />

Time-65 minutes<br />

Questions 1-5<br />

Percent of Section II srade-75<br />

Directions: Show all 5rour work. Indicate clearly the methods you use, because you will<br />

be gi'aded on the correctness of your method as well as on the accuracy of your results<br />

and exnlanations.<br />

L The table below shows the home run output of all Ameriean League and National<br />

League baseball teams during the 2000 season.<br />

American Leasue Home Runs<br />

Cleveland<br />

Kansas City<br />

Chicago White Sox<br />

Texas<br />

Anaheim<br />

New York Yankees<br />

Detroit<br />

Toronto<br />

Baltimore<br />

Minnesota<br />

Oakland<br />

Seattle<br />

Boston<br />

Tampa Bay<br />

221<br />

150<br />

2t6<br />

173<br />

236<br />

205<br />

177<br />

244<br />

184<br />

116<br />

239<br />

198<br />

167<br />

t62<br />

National Leazue Home Runs<br />

Colorado<br />

San Francisco<br />

Houston<br />

Cincinnati<br />

Atlanta<br />

St. Louis<br />

Pittsburgh<br />

Montreal<br />

Arizona<br />

New York Mets<br />

Florida<br />

Los Angeles<br />

Chicago Cubs<br />

San Diego<br />

Philadelphia<br />

Milwaukee<br />

161<br />

226<br />

249<br />

200<br />

t79<br />

235<br />

168<br />

178<br />

179<br />

198<br />

160<br />

2t1<br />

i83<br />

(a) In the area provided below, construct one histogram displaying the distribution of<br />

homerun output <strong>fo</strong>r all teams (both American and National Leagues). Describe<br />

the nature of the distribution noting the center of the distribution, skewness, and<br />

outliers (if any).<br />

183<br />

1AA<br />

ITT<br />

t77<br />

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Sample Examination Two Section II<br />

(b) Draw box plots <strong>fo</strong>r the data in each of the two leagues and identifl, the fivenumber<br />

summary <strong>fo</strong>r each plot. What comparisons can you make between the<br />

homerun outputs of the two ieagues?<br />

(c) Construct a back-to-back stemplot displaying the homerun outputs of teams in<br />

the two leagues,<br />

or<br />

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Section I Sample Examination Two<br />

2. A telecommunications company uses three different systems to produce the print shaft<br />

holder <strong>fo</strong>r its most popular fax machine. System A produces 50o/o of the shaft holders,<br />

System B produces 30% ofthe shaft holders, and System C produces 20% ofthe shaft<br />

holders. The percentages of defective shaft holders produced by each system are<br />

respectively, 3Vo, 4Yo and 5o/o.<br />

(a) If a shaft holder is selected at random, what is the probability that it is defective?<br />

(b) If a shaft holder is selected at random and <strong>fo</strong>und to be defective, what is the<br />

probability that it was produced by System A?<br />

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50 Sample Exarnination Two Section [I<br />

3. A Television Monitoring Group (TMG) claims that at least three out of every <strong>fo</strong>ur<br />

Americans believe that realitv-based television shorvs are untruthful. They tested their<br />

claim by using data from a recent Gallup poll ufiich indicated that in a sample of 1 ,015<br />

Americans, 812 thought the shows were either somewhat or totally untruthful.<br />

(a) Testthe claim of theTMC using a signifieance level of 0.0i. State cleariy your<br />

assumptions and u,hat test of hypothesis you are using. Identifu an appropriate<br />

p-r'alue and interpret vour results ri'itiriir the context of the problenr.<br />

(b) Construct a9SYo confidence interval to estimate the true proportion of Americans<br />

who thinli these shows are essentially untruthful.<br />

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Sectiosr II Sarnple Examination Two 51<br />

4. A survey was conducted recently in ten large American cities to<br />

there is any relationship between average weekday hotel rates and<br />

rates. The <strong>fo</strong>llowine data was collected.<br />

Daily Hotel Rate (x)<br />

(in dollars)<br />

149<br />

187<br />

17l<br />

r22<br />

lt)<br />

147<br />

128<br />

2r2<br />

168<br />

181<br />

(a) Construct a scatternlot <strong>fo</strong>r this data.<br />

(b) Use the scatterplot to determine if there<br />

variables.<br />

Daily Car Rental Rate (y)<br />

(in dollars)<br />

49<br />

50<br />

52<br />

49<br />

39<br />

44<br />

aa<br />

JI<br />

OJ<br />

40<br />

5l<br />

determine whether<br />

average car rental<br />

is a linear relationshio between the tu'o<br />

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52 Sample Examination Two Section II<br />

(c) If there is a linear relationship, numerically describe the strength of this<br />

relationship and construct a least squares regression model.<br />

(d) Find tlie residual associated with the point (168, 46).<br />

(e) What percent of the variation in car rental rates is explained by the regression of<br />

yonx?<br />

ol<br />

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Section II Sample Examination Two<br />

5. A medical research group is interested in comparing the effectiveness of two new<br />

medications in reducing cholesterol levels in adult males ranging in age from 35-65<br />

years of age who have exhibited elevated cholesterol levels <strong>fo</strong>r at least six months, Four<br />

hundred men with elevated cholesterol levels in this age group were randomly selected<br />

in New Ycrrk City and 340 men were randomly selected in Philadelphia. It is suspected<br />

that results will differ greatly between the two cities due to a recent 'heart health'<br />

initiative in Philadelphia. Describe a randomized block design to conduct this<br />

experiment.<br />

53<br />

ot<br />

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f,{ Sample Examination Two Seetion [I<br />

Section II<br />

Fart B<br />

Time-25 minutes<br />

Question 6<br />

Percent of Section II erade-25<br />

Direetions: Show'all your work. Indicate clearly the methods you use, because you wiil<br />

be graded on the correctness of your method as rvell as on the accuracy of your results<br />

and explanations.<br />

6. In 1 908 W. S. Gosset wrote a paper titled, "The Probable Error of a Mean". in the paper<br />

Gossett reported on the corn yieid using two different kinds of seeds. The first seed was<br />

the usual seed used by farmers in England at that time. The second seed type was kilndried.<br />

Each type of seed was planted in adjacent plots, accounting <strong>fo</strong>r 11 pairs of "split"<br />

plots. The data are given belorv. The numbers are in pounds per acre.<br />

Plot Regular Kiln-Dried<br />

1 903 20a9<br />

2 1935 1915<br />

J 1910 2011<br />

A<br />

L+ 2496 2463<br />

5 2 108 2180<br />

6 1961 1925<br />

7 2060 2122<br />

8 441 t482<br />

9 612 1542<br />

10 316 1443<br />

1t 5il 153 5<br />

The <strong>fo</strong>llowing computer outputs show the descriptive statistics of the two variables and<br />

a regression output which resulted from fitting a least squares regression line using<br />

yield from "regular" seed to predict yield from "kiln-dried" seed.<br />

Variable N Mean Medi-an TrMean StDev SE Mean<br />

Regular 11 1841 191-0 1-827 343 t_03<br />

Kiln-Dri 1l- 1875 L925 1858 333 t-00<br />

Variable Minimum Maximum Ql- Q3<br />

Regular l-31-6 2496 1511- 2060<br />

xiln-ori L443 2463 1535 2L22<br />

Predictor<br />

onstrant<br />

Ponrr'l rr<br />

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Coef StDev<br />

120 .4 LL6 .'l<br />

0.95293 0.06241<br />

R-Sq=l$.39 R-Sq (adj )<br />

=95.98<br />

T<br />

1-.03<br />

15 .21<br />

P<br />

0 "329<br />

0. 000


Section trI Sample Examination T\vo 55<br />

Below is a residual plot and a normal quantile plot of the residuals resulting from the<br />

regression.<br />

e<br />

E<br />

z<br />

2<br />

.2<br />

Residuals Versus REGULAR<br />

tesph3. is KLN-DRI)<br />

rso 2@ 25m<br />

REGULAR<br />

Normal Probabili\i Plot of the Residuals<br />

G.s@nse is KLN-oRl)<br />

Residual<br />

(a) Use side-by-side box plots to compare the corn yield <strong>fo</strong>r the two groups. Write a<br />

few sentences commenting on your display.<br />

(b) Can yield of "regular seed" be used to predict the yield of "kiln dried seed"?<br />

Give statistical justification to support your response.<br />

or reusrng<br />

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Sample Examination Two Section Itr<br />

(c) Is there a difference in yield betu,een the two types of seeds'/ Give statistical<br />

justification to support your response.<br />

or<br />

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