 A class of 400 students is divided into 2 sections of 200
each. Both sections are given a common exam. The following
is observed

Average 
SD 
Section 1 
85 
10 
Section 2 
45 
10 
Suppose all 400 scores are combined as one list. The SD of the
new list will be
 smaller than 10
 larger than 10
 equal to 10
 can't tell without knowing the entire list
 A study was made of the age at entrance of college freshman
to Duke. The SD turned out to be:
 1 month
 1 year
 5 years
 Given the group of numbers: 3, 7, 4, 6, 2, 2, 7, 3, 2. Which
of the following are the same?
 average
 range
 SD
 median
 mode
 The average temperature in Durham on the 11th day of May over
the last 10 years was 74 degrees F with an SD of 6 degrees F.
Temperature Centigrade is found by subtracting 32 degrees from
temperature Fahrenheit, then multiplying by 5/9. What were the
average and the SD of the temperature in Durham on the 11th day
of May expressed in degrees Centigrade.
 Draw two histograms, one with its average greater than its
median and the other with its median greater than its average.
Label which is which.
 A list of numbers has a normal distribution, an average of
10 and an SD of 2. What is the interquartile range?
 A teacher decides to test a new teaching method. In class
A she gives 'pop' quizzes at random intervals. In class B she
gives announced quizzes on alternating Mondays. At the end of
the class she gives a common exam to both classes with the following
results. She creates a contingency table classifying students
by whether they had mastered more or less than 90% of the material.
Class 
<90% 
>90% 
Total 
% scoring >90% 
A 
85 
65 
150 
43% 
B 
68 
32 
100 
32% 
Total 
153 
97 
250 

Then she decides to look at whether the effect was consistent
for upper and lower classmen. She found the following.
Fresh/Soph Class 
<90% 
>90% 
Total 
% scoring >90% 
A 
60 
15 
75 
20% 
B 
60 
15 
75 
20% 
Total 
120 
30 
150 

Jr/Sr Class 
<90% 
>90% 
Total 
% scoring >90% 
A 
25 
50 
75 
67% 
B 
8 
17 
25 
68% 
Total 
33 
67 
100 

 What is the confounding variable?
 Calculate a weighted average for the percentage in Class A
that mastered greater than 90% of the material taking into account
the confounding variable. Do the same for Class B.
 The ETS Verbal Aptitude Test is designed so that the scores
of high school seniors taking the test will have a normal distribution
with average 500 and SD 100. A college wants their students to
be in the top 12.5% for verbal aptitude. What minimum qualifying
score should they set?
 At one law school, the correlation between LSAT score and GPA
for firstyear students was 0.4. Average LSAT of those admitted
was 650 with an SD of 50; average GPA was 3.0 with an SD of 0.4.
Both scores approximately follow the normal curve. Draw a scatter
diagram to help answer the following questions.
 approximately what percentage of all students admitted was
above average on both the LSAT score and law school GPA?
 With the same averages and SD's, and the scores following the
normal curve, what is the highest that this percentage could be
at another law school? What would be the corresponding correlation?
____________% __________________Correlation
 Suppose .5 was added to the GPA of each student at the law
school. How would the correlation between LSAT and GPA change?
 increase
 decrease
 stay the same
 can't tell without further information
 A teaching assistant gives a quiz. There are 10 questions
on the quiz and no partial credit is given. After grading the
papers the TA writes down for each student the number of questions
the student got right and the number he got wrong. The average
number of correct answers is 6.4 with an SD of 2.0.
 What is the average and SD of the number of wrong answers?
____________Average ____________SD
 The correlation coefficient between the numbers of right and
wrong answers is
 0
 .5
 +.5
 1
 +1
 can't tell
 After being given a dose of a certain drug, the average
temperatures and blood pressures of 5 groups of 20 subjects were
recorded. The correlation for the 5 pairs of group averages was
+0.92. The relation between a subject's temperature and blood
pressure in the group is almost exactly a line. True or False?
 A doctor records, for 400 hospital patients selected at random,
the pair: (temperature when admitted, temperature 24 hours later).
He finds that the average temperatures are 101 degrees when admitted,
99 the next day. The SD is 1.5 degrees for temperatures when
admitted, 0.5 for those the next day. The correlation between
the two temperatures is 0.8. The scatter diagram is football
shaped.
 if a patient enters with temperature 103, what do you expect
his temperature to be the next day?
 The fact that the average temperature the day
after entering is 2 degrees less than upon admission is due
to the regression effect. True or False?
 As part of a large experimental course, a diagnostic quiz
is given at the outset of the course. At the end of the course,
the instructor collected the following statistics:
Diagnostic quiz (20 points possible): average=10, SD=4
Final exam (100 points possible): average=60, SD=15
r=0.6
Of those who scored 6 points on the diagnostic quiz, about what
percent scored below average on the final?
 A GPALSAT study shows that the slope for estimating LSAT
from GPA is about 100 LSAT points per GPA point. Which of the
following is correct?
 If one person has twice the GPA of another, his or her estimated
LSAT score is 100 points higher than the others. True or False?
 If two people differ by 1.5 points in GPA, you can expect their
LSAT scores to differ by about 150 points. True or False?
 A person with a GPA of 3.5 will score, on average, 3.5x100=350
on the LSAT. True or False?
 The SD of LSAT scores is 100xSD of GPA scores in the group
studied. True or False?
 A certain pregnancy test determines pregnancy with high probability.
In particular, if a woman is pregnant the chance the test will
give a positive reaction is 90%. If she isn't pregnant, the chance
it will give a negative reaction is 85%. Suppose a woman takes
the test and gets a negative result. The chance she is pregnant
is: ___________ or can not be determined
 An astronaut's oxygen supply comes from two independent sources.
Source A has probability 0.9 of working, and Source B has probability
0.8 of working. What is the probability that at least one of
the sources is working?
 A die is tossed twice. Given that the sum is greater than
7, what is the chance of getting a pair?
 There are 20 men and 5 women in a class. Each day one person
is chosen at random (with replacement).
 What is the chance that a woman will be chosen on any given day?
 What is the chance that a man is chosen on the first three days?
 What is the chance of choosing exactly two women in the first
five days?
 What is the chance of choosing at least two women in the first
five days?
 What is the chance of choosing a woman on the fifth day given
that you chose a man on each of the first four days?
 What is the chance of choosing a man on the first day and
a woman on the second day?
 What is the chance of choosing a man on the first day or a
woman on the second day?
 You want to find out about drug use among members of your
class, but you are sure that people will not respond honestly
if you ask them directly, so you set up a scheme such that each
classmate is given a private ticket. No one besides the receiver
knows what was on the ticket. 70% of the tickets have a S written
on them and 30% have an NS written on them. Those students receiving
an S ticket are to answer the question " Have you used an
illegal drug in the last week?" Those with an NS ticket
are to answer the question "Does your mother's phone number
end in an even digit?". In the class of 60, 25 respond yes
to their question and 35 respond no. Calculate the probability
that a classmate has used illegal drugs in the past week.
 In a city, 20% of the workers have incomes over $40,000 per
year. If 1600 workers are chosen at random with replacement,
what is the chance that between 320 and 336 of those chosen have
incomes over $40,000 per year?
 One hospital has 112 live births during the month of June,
another has 432. Which is likelier to have 55% or more male births
or are the chances equal? (Note: there is about a 52% chance for a
liveborn infant to be male.)
Hospital with 112 births 

Hospital with 432 births 
 In a certain precinct, 80% of the voters are Republican.
A simple random sample of size 400 is drawn (with replacement).
Each person in the sample is polled and the percentage of Republicans
in the sample is calculated. What is the chance that this percentage
is between 78% and 88%.
 In a simple random sample of 900 students at a major state
university, only 180 favor a return to the semester system. Find
a 95% confidence interval for the percentage of students in the
university favoring a return to the semester system.
 In 1990, the average of the daily maximum temperature at San
Francisco Airport was 64.4 degrees, with an SD of 7 degrees.
The standard error for the average is
A 95% confidence interval for the average daily maximum temperature
at San Francisco airport is 64.4 +/ 0.74 degrees. True or False?
 A large lecture course has 1000 students. On a midterm exam,
the class average was 50 with an SD of 10. For one section of
25 students the section average was 60. It is suggested that
the early morning section has more serious students and would
therefor have higher scores.
 Formulate the null hypothesis
 compute z and P
 Can this higher average be reasonably explained by chance
variation? Justify your answer.
 To find our whether students should be required to take a
statistics course, a campus poll is taken; the results are shown
below:

Fresh/Soph 
Jr/Seniors 
Totals 
Should 
197 
195 
392 
Should not 
233 
175 
408 
Totals 
430 
370 
800 
 Calculate the relative risk.
 Interpret the relative risk.
 Calculate the odds ratio.
 Using the data given, test the hypothesis that responses do
not differ according to class in the total population of
students. Use a Chisquare test with a 0.05 level of
significance.
 You are hired by the university to estimate the % of students
that oppose the alcohol policy at Duke. How many students should
you sample to be 95% confident of falling within +/ 2 percentage
points of the true population percentage. Assume a pilot study
has been done estimating the percentage to be 50%.
 What do each of the following symbols stand for in standard
statistical practice?
= ______________________________________
= ______________________________________
= ______________________________________
 A friend tells you he has a coin that lands heads 25%, 50%,
or 75% of the time, but he does not tell you which. Before seeing
any data you assume that each possibility is equally likely. He
then lets you toss the coin 8 times, and it lands heads 7 times.
 What is your posterior probability that p=.5?
 What is your prediction for the probability that the coin will
land heads the next time it is tossed?
 Suppose you wanted to test H0:p=.5 against HA:p>.5. What
is the observed pvalue?
 In two sentences or less explain why the answers to a and d
are different.
 A random sample of graduate students at Duke were asked how
much they expected to make upon taking their first job after graduation.
The students were categorized by political party affiliation
(1=Democrat 2=Independent 3=Other 4=Republican). A researcher
wanted to know if average expected salary differed by political
party affiliation. Below is the output for an analysis of variance.
Answer the questions below the output:
General Linear Models Procedure
Class Level Information
Class Levels Values
Q4 4 1 2 3 4
Number of observations in data set = 38
NOTE: Due to missing values, only 35 observations can be used in this
analysis.
General Linear Models Procedure
Dependent Variable: Q6 Expected salary upon graduation
Sum of Mean
Source DF Squares Square F Value Pr > F
Model 3 1.287E+09 4.291E+08 2.84 0.0541
Error 31 4.687E+09 1.512E+08
Corrected Total 34 5.974E+09
RSquare C.V. Root MSE Q6 Mean
0.215454 30.70738 12296 40043
Source DF Type I SS Mean Square F Value Pr > F
Q4 3 1.287E+09 4.291E+08 2.84 0.0541
Source DF Type III SS Mean Square F Value Pr > F
Q4 3 1.287E+09 4.291E+08 2.84 0.0541
Tukey's Studentized Range (HSD) Test for variable: Q6
NOTE: This test controls the type I experimentwise error rate,
but generally has a higher type II error rate than REGWQ.
Alpha= 0.05 df= 31 MSE= 1.5119E8
Critical Value of Studentized Range= 3.838
Minimum Significant Difference= 21703
WARNING: Cell sizes are not equal.
Harmonic Mean of cell sizes= 4.729064
Means with the same letter are not significantly different.
Tukey Grouping Mean N Q4
A 47667 12 2
A
A 42000 5 4
A
A 35000 2 3
A
A 34344 16 1
 What is the null hypothesis the researcher is testing?
 What are the assumptions necessary to make this a valid test?
 What does the Mean Square for the Model tell us about the
variability in our data?
 What does the Mean Square for the Error tell us about the
variability in our data?
 How is the Fstatistic calculated? (Use the numbers on the
output to illustrate.)
 What is the conclusion from this test? Justify your answer.
 If you worked in pairs on your data project, list the percentage
of the project completed by yourself ______________% and the percentage
completed by your partner _____________%.
 Honor Code: My data project was my own work, not the work
of someone else.
Signature _______________________________