STAT 100 Midterm 1 Sample Exam - Spring 2013

STAT 100
Midterm 1
Sample Exam - Spring 2013
QUESTION 1 (6 pts)
3417 people were recently selected at random from all adult taxpayers in Canada and answered
questions about the Canada Revenue Agency (CRA) assessments.
A. (1 pt) What was the population for the study?
B. One question was, “Do you feel that CRA assessments are accurate?” 2137 answered
“Yes”.
a. (1 pt) Estimate the percentage of the population that feels that the CRA
assessments are accurate.
b. (1 pt) Find the margin of error for the estimate.
c. (1 pt) Explain what the margin of error tells you about the population here.
C. (2 pts) Suppose that three years ago another survey of about the same size asked the
same question and got an estimate that was statistically significantly lower than the
current estimate. Between that survey and this one, CRA began a new program to
improve their assessment accuracy.
Can they claim that the new program has been successful? Explain.
STAT 100 Midterm 1 – Sample Exam
QUESTION 2 (4 pts)
The table at right lists the number of grouse sighted
by a wildlife manager at a certain wildlife park
over 5 years. He would like to try to figure out
whether the different ages (Adult or Immature) and
genders (Female and Male) have any effect on the
number of sightings.
A. List any response variables:
B. List any explanatory variables:
C. Select any variable and list its values:
Year
1993
1993
1993
1993
1994
1994
1994
1994
1995
1995
1995
1995
1996
1996
1996
1996
1997
1997
1997
1997
1998
1998
1998
1998
Age
I
I
F
F
I
I
F
F
I
I
F
F
I
I
F
F
I
I
A
A
I
I
A
A
Gender
M
F
F
M
M
F
F
M
M
F
F
M
M
F
F
M
M
F
F
M
M
F
F
M
Sightings
103
99
139
85
145
168
298
122
68
93
205
87
105
148
171
69
147
169
175
95
110
119
150
87
QUESTION 3 (2 pts)
Below are some measurements and corresponding instruments for each one indicate whether it is
likely to be a valid measurement (in the blank, respond YES for valid, NO for not valid or
MAYBE for not enough information)
A.
Using movie rating (G, PG, 14A, 18A, R) to measure the appropriateness of
a film for children
B.
Using length of a movie as a measure of its quality
C.
Using an x-ray as a measure of the presence of a fracture
D.
Using a written driver’s test as a measure of driving ability
2
STAT 100 Midterm 1 – Sample Exam
QUESTION 4 (6 pts)
Please indicate the correct answer from
A. Which of the following is not true of a simple random sample of size 1000 chosen from a
population of size 4,000,000?
a) Every individual in the population has the same chance of selection as every other
individual.
b) Every set of 1000 individuals has the same chance of being the sample as every other
set of 1000 individuals.
c) Every individual of the population has chance 1 in 1000 of being included in the
sample.
d) Every set of 500 individuals has the same chance of being included in the sample as
every other set of 500 individuals.
B. Bias in a sampling method is
a. any error in the sample result, that is, any deviation of the sample result from the truth
about the population.
b. the random error due to using chance to select a sample.
c. any error due to practical difficulties such as contacting the subjects selected.
d. any systematic error that tends to occur in the same direction every time you use this
sampling method.
e. racism or sexism on the part of those who take the sample.
C. A sportswriter wants to know how strongly Columbus, Ohio residents support building a new
stadium for the local minor league baseball team, the Columbus Clippers. She stands outside
the stadium before a game and interviews the first 25 people who enter the stadium. The
newspaper asks you to comment on their survey of local opinion. You say
a. this is a simple random sample. It gives very accurate results.
b. this is a simple random sample. The results are not biased, but the sample is so small
that variation will be high.
c. this is a census, because all fans had a chance to be asked. It gives very accurate
results.
d. the sampling method is biased. It will almost certainly overestimate the level of
support among all Columbus, Ohio residents.
e. the sampling method is biased. It will almost certainly underestimate the level of
support among all Columbus, Ohio residents.
3
STAT 100 Midterm 1 – Sample Exam
QUESTION 5 (6 pts)
A study was performed on the effects of distractions on studying. A room at a university
was set up with a sound system and a TV. Student volunteers who entered the room were
exposed to either (1) loud rock music, (2) soft baroque music, (3) an adventure movie on the
TV, or (4) quiet (no TV or music).
The student volunteers first took a brief pre-test. The students were placed into groups
according to scores on the pre-test: the top 4 formed the first group, the next 4 highest
formed the second group, and so on. There were 20 volunteers, so there were 5 groups.
From each group, one student was exposed to the loud rock, one to the soft baroque, one to
the TV, and one to the quiet. Every student was given some materials to read and study for
an hour. At the end of the hour, each student took a final test on the materials.
A. (1 pt) What kind of study is this?
a. an observational study
b. an experiment
c. a census
d. a survey
e. None of the above
B. (1 pt) What is the response variable?
a. the type of distraction
b. the final test score
c. the pre-test score
d. the room
e. none of the above
C. (1 pt) What purpose does the pre-test serve?
a. it is the response variable
b. it is used to create blocks
c. it is the treatment variable
d. it is the randomization device
e. none of the above
D. (1 pt) The test that students took after the study period was
a. a block
b. an instrument
c. a randomization
d. a census
e. none of the above
4
STAT 100 Midterm 1 – Sample Exam
QUESTION 5 Cont’d
E. (1 pt) The population for this study is:
a. Monkeys
b. Students at the same university
c. Adults
d. All university students
e. None of the above
F. (1 pt) Suppose that the average final test score in among students exposed to loud
rock was statistically significantly lower than the average among students who
listened to soft baroque. Which of the following conclusions can be made?
a.
b.
c.
d.
e.
Modern music is more distracting than classical music
Rock music is more distracting than baroque music
Any kind of music is distracting
None the study is fundamentally flawed
None of the above
QUESTION 6 (3 pts)
Dinehere.ca is a website devoted to customer ratings for restaurants in the lower mainland.
People can create a username on the site using an e-mail address and password, and then can rate
restaurants and real others’ ratings. Restaurants are scored on a 1-5 scale in 4 separate areas:
Food, Service, Value, and Ambiance. The rater’s Overall score for a restaurant is calculated
automatically from the average of these 4 areas’ scores. Restaurants are then rated on the basis
of the average Overall score across all raters. A username may rate each restaurant only once
(only the username’s most recent review counts toward the restaurant’s average).
A. (1 pt) What method of data collection is this?
B. (2 pts) Comment on the general quality and reliability of a restaurant’s rating, indicating
any problems you see that may arise.
5
STAT 100 Midterm 1 – Sample Exam
QUESTION 7 (5 pts)
A. (2 pts) If a study is conducted ethically, which of the following are true? (Choose all
that apply).
a. The researchers use randomization to select participants
b. The researchers will not release the names of individuals who participated in the
study
c. The researchers use margins of error to report results
d. Subjects are given a choice whether to participate
B. (1 pt) Why use a placebo in an experiment? (Choose one)
a. It helps to keep patients from getting sick
b. It helps to estimate how much response the other treatments are actually causing
c. It helps to prevent bias by the researcher
d. It helps to keep the experiment more random
e. All of the above
f. None of the above
C. (1 pt) If an experiment is not blinded, what should you be worried about? (Choose one)
a. Subjects in one treatment group may be inherently quite different from subjects in
other treatment groups.
b. The comparisons of different treatment groups may not be very accurate
c. The comparisons of different treatments’ effects may not be very precise
d. The responses may not be kept confidential
e. All of the above
f. None of the above
D. (1 pt) Prescription drug safety trials are (almost) always conducted on a sample of adult
male volunteers. This is a problem when the time comes to prescribe the drugs to the
general public because (Choose one)
a. There are not enough adult males left to take the drugs who haven’t already been
exposed to them
b. The samples are too small for the results to apply to the general public
c. We can’t be sure that women and children will react to the drugs the same way
that the adult males did
d. All of the above
e. None of the above
6