Transcript Review 4.1-4.4 - Edwardsville School District 7

Chapter 4
Potpourri
Surveys vs Experiments
Surveys vs Experiments
Surveys vs Experiments
Surveys vs Experiments
Surveys vs Experiments
Surveys vs Experiments
Surveys vs Experiments
Surveys vs Experiments
Surveys vs Experiments
Eliminates selection bias
Surveys vs Experiments
Surveys vs Experiments
Surveys vs Experiments
Surveys vs Experiments
Surveys vs Experiments
Surveys vs Experiments
Surveys vs Experiments
Surveys vs Experiments
Sampling
1. What is the difference between the
groups for cluster sampling and stratified
random sampling?
Sampling
1. What is the difference between the
groups for cluster sampling and stratified
random sampling?
Clusters: similar characteristics; each group
is representative of population
Stratified: different characteristics
--level of income, political party
2. What is the key to reducing confounding
in an experiment?
2. What is the key to reducing confounding
in an experiment?
Assign treatments at random to
experimental units
3. Suppose pairs of identical twins agree to
participate in an experiment to test the
effect of salt on blood pressure. It is
decided by a coin flip which of the twins
will consume a high-salt diet and which will
consume a low-salt diet. The response
variable will be their blood pressure after
ten weeks on the diet. This is an example
of ___________.
3. Suppose pairs of identical twins agree to
participate in an experiment to test the effect of
salt on blood pressure. It is decided by a coin flip
which of the twins will consume a high-salt diet
and which will consume a low-salt diet. The
response variable will be their blood pressure
after ten weeks on the diet. This is an example
of
A.
a completely randomized design
B.
a randomized paired comparison design
(matched pairs)
C.
a randomized paired comparison design with
repeated measures on the same subject
D.
stratification
E.
two-stage cluster sampling
3. Suppose pairs of identical twins agree to
participate in an experiment to test the effect of
salt on blood pressure. It is decided by a coin flip
which of the twins will consume a high-salt diet
and which will consume a low-salt diet. The
response variable will be their blood pressure
after ten weeks on the diet. This is an example
of
A.
a completely randomized design
B.
a randomized paired comparison design
(matched pairs)
C.
a randomized paired comparison design with
repeated measures on the same subject
D.
stratification
E.
two-stage cluster sampling
4. When the effects of two variables on a
response variable cannot be distinguished
from each other, the variables are said to
be __________.
4. When the effects of two variables on a
response variable cannot be distinguished
from each other, the variables are said to
be
A. biased
B. blocked
C. confounded
D. stratified
E. outliers
4. When the effects of two variables on a
response variable cannot be distinguished
from each other, the variables are said to
be
A. biased
B. blocked
C. confounded
D. stratified
E. outliers
5. To test a new skin rash drug, researchers
decide to administer both the new drug
and the standard drug, in random order, to
each patient in the experimental study.
That is, the researchers carrying out the
study plan to use a randomized paired
comparison design with repeated
measures. What is the main weakness of
this design?
5. To test a new skin rash drug, researchers
decide to administer both the new drug and the
standard drug, in random order, to each patient
in the experimental study. That is, the
researchers carrying out the study plan to use a
randomized paired comparison design with
repeated measures. What is the main weakness
of this design?
A. It did not use blocking.
B. The resulting data would show evidence of too
much within-treatment variability.
C. The resulting data would show evidence of too
much between-treatment variability.
D. There was no control group.
E. The effect of the first drug may not have worn
off before the second drug was administered.
5. To test a new skin rash drug, researchers decide to
administer both the new drug and the standard drug, in
random order, to each patient in the experimental study.
That is, the researchers carrying out the study plan to
use a randomized paired comparison design with
repeated measures. What is the main weakness of this
design?
A. It did not use blocking.
B. The resulting data would show evidence of too much
within-treatment variability.
C. The resulting data would show evidence of too much
between-treatment variability.
D. There was no control group.
E. The effect of the first drug may not have worn off
before the second drug was administered.
6. Suppose you want to study the effect of
calculator use on the mathematics course
grade for sixth-grade students in a
district’s single middle school. In the
upcoming school year, the middle school
will have a total of 500 sixth-grade
students.
6. Suppose you want to study the effect of
calculator use on the mathematics course grade
for sixth-grade students in your district’s single
middle school. In the upcoming school year, the
middle school will have a total of 500 sixth-grade
students.
Now, suppose that you plan to ask each student
whether he or she uses a calculator and then
compare the mean mathematics course grade
for each group. Is this an observational study or
an experiment? Explain.
Suppose that you plan to ask each student
whether he or she uses a calculator and
then compare the mean mathematics
course grade for each group. Is this an
observational study or an experiment?
Explain.
It’s an observational study because the
two treatments (using/not using a
calculator) are not randomly assigned
to the students.
7. Identify which type of sampling design is
being used in each scenario.
a.A school administrator randomly selects
12 classes from your school and then
randomly selects 5 students from each
class to study a school library issue.
7. Identify which type of sampling design is
being used in each scenario.
a. A school administrator randomly selects
12 classes from your school and then
randomly selects 5 students from each
class to study a school library issue.
two-stage cluster sample
7. Identify which type of sampling design is
being used in each scenario.
b. A school administrator uses random
numbers to select a sample of 60 students
from the roster of students enrolled in your
school.
7. Identify which type of sampling design is
being used in each scenario.
b. A school administrator uses random
numbers to select a sample of 60 students
from the roster of students enrolled in your
school.
simple random sample
c. A school administrator gets a sample of
60 students from your school by randomly
selecting 15 freshmen, 15 sophomores, 15
juniors, and 15 seniors.
c. A school administrator gets a sample of
60 students from your school by randomly
selecting 15 freshmen, 15 sophomores, 15
juniors, and 15 seniors.
stratified random sample
d. A school administrator uses the roster
of students enrolled in your school to
select a sample of students by choosing a
person randomly from among the first 20
and then taking every 20th name on the
roster thereafter.
d. A school administrator uses the roster of
students enrolled in your school to select
a sample of students by choosing a
person randomly from among the first 20
and then taking every 20th name on the
roster thereafter.
systematic sample with random start
8. Blocking will be effective if
A. all units in one block receive the same
treatment
B. each subject receives all treatments
C. units are grouped so that each block contains
units that are different
D. units are grouped so that each block contains
units that are similar
E. units are grouped so that each block is
representative of the population
8. Blocking will be effective if
A. all units in one block receive the same
treatment
B. each subject receives all treatments
C. units are grouped so that each block contains
units that are different
D. units are grouped so that each block
contains units that are similar
E. units are grouped so that each block is
representative of the population
9. What is the main purpose of random
selection in a sample survey?
9. What is the main purpose of random
selection in a sample survey?
To reduce bias and get a representative
sample from the population
10. Compared to simple random sampling,
stratified sampling can help accomplish several
goals. Which of these goals does it not
advance?
A. reduce the variability associated with a statistic
such as the sample mean
B. improve the precision of the results
C. provide good information on each stratum
D. make it unnecessary to use randomization
E. make it easier to take a sample
10. Compared to simple random sampling,
stratified sampling can help accomplish several
goals. Which of these goals does it not
advance?
A. reduce the variability associated with a statistic
such as the sample mean
B. improve the precision of the results
C. provide good information on each stratum
D. make it unnecessary to use randomization
E. make it easier to take a sample
11. There are two types of bias in sampling problems: bias
due to the improper selection of sampling units and bias
due to incorrect response or nonresponse. Which of
these is least likely to help protect against bias?
A. random selection of sampling units
B. cluster sampling as compared to simple random
sampling
C. following up with those who do not respond to the initial
survey
D. designing clear and unambiguous questions
E. constructing a good sampling frame
11. There are two types of bias in sampling problems: bias
due to the improper selection of sampling units and bias
due to incorrect response or nonresponse. Which of
these is least likely to help protect against bias?
A. random selection of sampling units
B. cluster sampling as compared to simple random
sampling
C. following up with those who do not respond to the initial
survey
D. designing clear and unambiguous questions
E. constructing a good sampling frame
12. In a northern state, these two variables
are strongly associated. Each case is a
week during the previous year. What
possible lurking variable could be
responsible for this association?
I. the number of snow shovels sold at a local
hardware store during the week
II.the number of school closures during that
same week
12.
I. the number of snow shovels sold at a local
hardware store during the week
II. the number of school closures during that same
week
The number of inches of snow. As the number of
inches of snow increases, more and more
schools close down and more equipment for
shoveling snow is sold at hardware stores.
13. Which of these is not a purpose or a
characteristic of an experiment?
A. to compare two or more treatments
B. to estimate the parameters of a fixed, welldefined population
C. to establish cause and effect by comparing the
effect of treatments on the response
D. random assignment of treatments to subjects
E. replication of each treatment on at least two
subjects
13. Which of these is not a purpose or a
characteristic of an experiment?
A. to compare two or more treatments
B. to estimate the parameters of a fixed, welldefined population
C. to establish cause and effect by comparing the
effect of treatments on the response
D. random assignment of treatments to subjects
E. replication of each treatment on at least two
subjects
14. Which of these will help protect against bias?
A. using a sampling process for its convenience
B. allowing volunteers to be in the sample
C. using randomization in choosing the units for
the sample
D. using expert judgment in choosing the units for
the sample
E. performing an observational study
14. Which of these will help protect against bias?
A. using a sampling process for its convenience
B. allowing volunteers to be in the sample
C. using randomization in choosing the units
for the sample
D. using expert judgment in choosing the units for
the sample
E. performing an observational study
15. Which of these is the definition of a biased sampling
method?
A. a method that results in estimates that are too high (or
too low) on the average
B. a method that usually results in estimates that are too
high (or too low)
C. a method that allows people to decide for themselves
whether to be in the sample
D. a method that results in a simple random sample
E. a method that results in nonrepresentative samples
some of the time, but accurate estimates on the average
15. Which of these is the definition of a biased sampling
method?
A. a method that results in estimates that are too high
(or too low) on the average
B. a method that usually results in estimates that are too
high (or too low)
C. a method that allows people to decide for themselves
whether to be in the sample
D. a method that results in a simple random sample
E. a method that results in nonrepresentative samples
some of the time, but accurate estimates on the average
16. In an experiment, if two variables are
confounded, which of these statements is true?
A. One of the variables must be a lurking variable.
B. The variables will have a correlation coefficient
greater than ±0.5.
C. There is a clear indication that a placebo effect
is present in the experiment.
D. The investigator cannot separate the effect of
the variables on a response variable.
E. None of these is true.
16. In an experiment, if two variables are
confounded, which of these statements is true?
A. One of the variables must be a lurking variable.
B. The variables will have a correlation coefficient
greater than ±0.5.
C. There is a clear indication that a placebo effect
is present in the experiment.
D. The investigator cannot separate the effect
of the variables on a response variable.
E. None of these is true.
17. In order to assess the membership’s attitudes
about a new Supreme Court decision, a local
bar association selects a simple random sample
of 100 lawyers from its membership list. Surveys
are delivered to the selected lawyers. Only 63 of
the lawyers return their surveys. Which of these
is of great concern in this situation?
17. In order to assess the membership’s attitudes about a
new Supreme Court decision, a local bar association
selects a simple random sample of 100 lawyers from its
membership list. Surveys are delivered to the selected
lawyers. Only 63 of the lawyers return their surveys.
Which of these is of great concern in this situation?
A. Nothing is known about the parameters of population
interest.
B. Nothing is stated regarding the methodology of the
simple random sample.
C. There may be a problem with the sampling frame.
D. There may be a problem with nonresponse bias.
E. None of these statements is of concern.
17. In order to assess the membership’s attitudes about a
new Supreme Court decision, a local bar association
selects a simple random sample of 100 lawyers from its
membership list. Surveys are delivered to the selected
lawyers. Only 63 of the lawyers return their surveys.
Which of these is of great concern in this situation?
A. Nothing is known about the parameters of population
interest.
B. Nothing is stated regarding the methodology of the
simple random sample.
C. There may be a problem with the sampling frame.
D. There may be a problem with nonresponse bias.
E. None of these statements is of concern.
Questions?