Question 1

Aggressiveness A recent study evaluated elementary age children for aggressiveness. This
study found that the children who played video games were more likely to engage in
aggressive or violent play at school. The researchers said the difference was statistically
significant.
a. Briefly explain what "statistically significant" means in this context.
b. The news media reported that this study proved that playing computer games causes
children to be aggressive or violent. Briefly explain why this conclusion is not justified.
c. But perhaps it is true. We wonder if playing computer games can lead to aggressive or
violent behavior in elementary school children. We find 50 young children whose families
volunteer to participate in our research. Design an appropriate experiment. (You need not
explain how to randomize.)

Accepted Answer

The answer of Aggressiveness A recent study evaluated elementary age...

Question 2

Which is true about randomized experiments?
I. Randomization reduces the effects of confounding variables.
II. Random assignment of treatments allows results to be generalized to the larger population.
III. Blocking can be used to reduce the within-treatment variability.
A) I only
B) I, II, and III
C) II only
D) III only
E) I and III

Accepted Answer

Randomization helps control confounding variables (I), and blocking reduces within-treatment variability (III). However, random assignment does not ensure generalizability to a larger population (II).

Question 3

The principal of a small elementary school wants to select a simple random sample of 24 students.
The school has 12 classrooms with 18 students in each class. She decides to randomly select two
Students from each classroom. Is this a simple random sample?
A) No, because not all combinations of 24 students could have been chosen.
B) Yes, because each student had an equal chance to be selected.
C) No, because each student did not have an equal chance of being selected.
D) Yes, because a stratified sample is a type of simple random sample.
E) Yes, because the students were selected at random.

Accepted Answer

A simple random sample requires that every possible combination of 24 students has an equal chance of being selected, which is not the case here since the selection is constrained to two students per classroom.

Question 4

In an experiment the primary purpose of blocking is to reduce
A) confounding.
B) randomness.
C) variation.
D) undercoverage.
E) bias.

Accepted Answer

Blocking is used in experiments to reduce variation by accounting for known sources of variability, allowing for more precise estimates of treatment effects.

Question 5

A company has tried to improve the effectiveness of its dishwashing detergent and wants to see if it
Works better than the original formula. They use 6 identical new dishwashers and load them
Identically with dirty dishes. Three packs of each of the two types of detergent are used, and they
Are randomly assigned to one of the six dishwashers. After the load is run, they rate each load for
Overall cleanliness. Which of the following is true?
A) The response variable is the type of detergent.
B) The explanatory variable is the different dishwashers.
C) A control group with no detergent at all is needed.
D) Because each brand is used in three dishwashers, replication is used properly.
E) Blinding is impossible in this experiment because they must be able to see the dishes.

Accepted Answer

The answer of A company has tried to improve the...

Question 6

Preservative Leather furniture used in public places can fade, crack, and deteriorate
rapidly. An airport manager wants to see if a leather preservative spray can make the
furniture look good longer. He buys eight new leather chairs and places them in the
waiting area, four near the south-facing windows and the other four set back from the
windows as shown. He assigned the chairs randomly to these spots.  
a. Use the random numbers given to decide which chairs to spray. Explain your method
clearly.  
b. Briefly explain why your assignment strategy is important in helping the manager assess
the effectiveness of the leather preservative.

Accepted Answer

The answer of Preservative Leather furniture used in public places...

Question 7

It was discovered that a larger proportion of children who slept with nightlights later developed
Nearsightedness, compared to children who did not sleep with nightlights. The headlines read,
"Leaving a light on for you children causes nearsightedness!" Later it was pointed out that
Nearsighted people have more trouble seeing in the dark and are more likely to leave lights on at
Night for their kids. And those same nearsighted parents are likely to have nearsighted kids. This is
An example of
A) a control group.
B) a randomized block design.
C) a lurking variable.
D) a placebo.
E) bias.

Accepted Answer

A lurking variable is a variable that is not controlled for in an experiment but that can affect the results. In this case, the lurking variable is the parents' nearsightedness.

Question 8

To check the effect of cold temperatures on the battery's ability to start a car researchers purchased
A battery from Sears and one from NAPA. They disabled a car so it would not start, put the car in a
Warm garage, and installed the Sears battery. They tried to start the car repeatedly, keeping track of
The total time that elapsed before the battery could no longer turn the engine over. Then they
Moved the car outdoors where the temperature was below zero. After the car had chilled there for
Several hours the researchers installed the NAPA battery and repeated the test. Is this a good
Experimental design?
A) No, because they should have tested other brands of batteries, too.
B) No, because the car and the batteries were not chosen at random.
C) No, because temperature is confounded by brand.
D) Yes
E) No, because they should have tested more temperatures.

Accepted Answer

The experiment confounds the effect of temperature with the brand of the battery, as each brand was tested under different temperature conditions.

Question 9

In an experiment the primary purpose of blocking is to
A) reduce the between-treatment variation.
B) reduce bias.
C) eliminate confounding variables.
D) eliminate the need for random assignment of treatments.
E) reduce the within-treatment variation.

Accepted Answer

The answer of In an experiment the primary purpose of...

Question 10

Candy packaging Marketing researchers wonder if the color and type of a candy's
packaging may influence sales of the candy. They manufacture test packages for chocolate
mints in three colors (white, green, and silver) and three types (box, bag, and roll).
Suspecting that sales may depend on a combination of package color and type, the
researchers prepare nine different packages, then market them for several weeks in
convenience stores in various locations. In this experiment.
a. what are the experimental units?
b. how many factors are there?
c. how many treatments are there?
d. what is the response variable?

Accepted Answer

The answer of Candy packaging Marketing researchers wonder if the...

Question 11

Can watching a movie temporarily raise your pulse rate? Researchers have 50 volunteers check
Their pulse rates. Then they watch an action film, after which they take check their pulse rates once
More. Which aspect of experimentation is present in this research?
A) none of these
B) a control group
C) a placebo
D) blinding
E) randomization

Accepted Answer

The experiment lacks a control group, placebo, blinding, and randomization. It simply measures pulse rates before and after watching a movie without these experimental controls.

Question 12

Public opinion A member of the City Council has proposed a resolution opposing
construction of a new state prison there. The council members decide they want to assess
public opinion before they vote on this resolution. Below are some of the methods that are
proposed to sample local residents to determine the level of public support for the
resolution. Match each with one of the listed sampling techniques.
a. Place an announcement in the newspaper asking people to call their council
representatives to register their opinions. Council members will tally the calls they receive.
b. Have each council member survey 50 friends, neighbors, or co-workers.
c. Have the Board of Elections assign each voter a number, then select 400 of them using a
random number table.
d. Go to a downtown street corner, a grocery store, and a shopping mall; interview 100
typical shoppers at each location.
e. Randomly pick 50 voters from each election district.
f. Call every 500th person in the phone book.
g. Randomly pick several city blocks, then randomly pick 10 residents from each block.
h. Randomly select several city blocks; interview all the adults living on each block. $$\begin{array} { | l | l | } 
\hline 1 & \text { cluster } \
\hline 2 & \text { convenience } \
\hline 3 & \text { judgment } \
\hline 4 & \text { multistage } \
\hline 5 & \text { simple (SRS) } \
\hline 6 & \text { stratified } \
\hline 7 & \text { systematic } \
\hline 8 & \text { voluntary response } \
\hline
\end{array}$$

Accepted Answer

The answer of Public opinion A member of the City...

Question 13

A Columbia University study linked soda consumption to behavior problems in children.
Researchers examined data from a previous study that followed 2929 mother-child pairs. One
Survey asked about behaviors of the child and also about soda consumption. They found that the
More soda the kids drank, the more behavior problems they had. What aspect of a well-designed
Experiment is absent from this study?
A) blinding
B) a control group
C) randomization
D) all of these
E) a placebo

Accepted Answer

The study lacks all three aspects of a well-designed experiment: blinding, a control group, and randomization.

Question 14

Telephone poll The City Council decides to conduct a telephone poll. Pollsters ask a
carefully chosen random sample of adults this question: "Do you favor the construction of a
new prison to deal with the high level of violent crime in our State?" In what way might the
proportion of "Yes" answers fail to accurately reflect true public opinion? Explain briefly.
What kind of bias is this?

Accepted Answer

The answer of Telephone poll The City Council decides to...

Question 15

Which is important in designing a good experiment?
I. Randomization in assigning subjects to treatments.
II. Control of potentially confounding variables.
III. Replication of the experiment on a sufficient number of subjects.
A) II and III
B) I and III
C) I and II
D) I only
E) I, II, and III

Accepted Answer

Randomization, control of confounding variables, and replication are all essential components of a well-designed experiment to ensure valid and reliable results.

Question 16

Twenty dogs and 20 cats were subjects in an experiment to test the effectiveness of a new flea
Control chemical. Ten of the dogs were randomly assigned to an experimental group that wore a
Collar containing the chemical, while the others wore a similar collar without the chemical. The
Same was done with the cats. After 30 days veterinarians were asked to inspect the animals for fleas
And evidence of flea bites. This experiment is…
A) randomized block, blocked by type of collar
B) completely randomized with one factor: the species of animal
C) completely randomized with two factors
D) completely randomized with one factor: the type of collar
E) randomized block, blocked by species

Accepted Answer

The experiment is a randomized block design, blocked by species, as the dogs and cats were separately randomized into treatment and control groups.

Question 17

Does Procellera Antimicrobial Wound Dressing help injuries heal faster? Researchers checked
Records of 38 patients who had been treated for acute or chronic wounds between 2010 and 2012.
They found that those who had been treated with Procellera
Healed almost twice as fast. This is a
A) matched experiment
B) retrospective study
C) prospective study
D) randomized experiment
E) survey

Accepted Answer

The study involves analyzing past records of patients who were treated between 2010 and 2012, making it a retrospective study.

Question 18

A school district administrator sent a survey to all teachers in the district. Only 30% of the teachers
Responded to the survey. Which of the following is true?
I. The people that did not responded are likely to be similar to those that did so he should use them
As the sample.
II. This survey design suffered from non-response bias.
III. Because he sent the survey to everyone, this is a census and the results can be applied to the
Whole population.
A) II and III only
B) I only
C) II only
D) I, II, and III
E) I and II only

Accepted Answer

The survey suffered from non-response bias because only 30% of teachers responded, which may not represent the views of the entire population. It is not a census because not everyone responded.

Question 19

Which of these is not an advantage of using a stratified sample instead of a simple random sample?
A) the stratified sample eliminates the need for randomization
B) the stratified sample reduces sample to sample variability
C) the stratified sample reduces bias
D) the stratified random sample allows you to get information about each stratum
E) the stratified sample allows you to get more reliable estimates using the same sample size

Accepted Answer

The answer of Which of these is not an advantage...

Question 20

M&Ms The Mars candy company starts a marketing campaign that puts a plastic game
piece in each bag of M&Ms. 25% of the pieces show the letter "M", 10% show the symbol
"&", and the rest just say "Try again". When you collect a set of three symbols "M", "&", and
"M" you can turn them in for a free bag of candy. About how many bags will a consumer
have to buy to get a free one? Use a simulation to find out.
a. Explain how you will use the random numbers listed below to conduct your simulation.
b. Carefully label your simulation for 2 trials.  
c. State your conclusion.

Accepted Answer

The answer of M&Ms The Mars candy company starts a...

Quiz 8: Regression, Associations, and Predictive Modeling

Which is true about randomized experiments? I. Randomization reduces the effects of confounding variables. II. Random assignment of treatments allows results to be generalized to the larger population. III. Blocking can be used to reduce the within-treatment variability.

The principal of a small elementary school wants to select a simple random sample of 24 students. The school has 12 classrooms with 18 students in each class. She decides to randomly select two Students from each classroom. Is this a simple random sample?

In an experiment the primary purpose of blocking is to reduce

In an experiment the primary purpose of blocking is to

Can watching a movie temporarily raise your pulse rate? Researchers have 50 volunteers check Their pulse rates. Then they watch an action film, after which they take check their pulse rates once More. Which aspect of experimentation is present in this research?

Which is important in designing a good experiment? I. Randomization in assigning subjects to treatments. II. Control of potentially confounding variables. III. Replication of the experiment on a sufficient number of subjects.

Does Procellera Antimicrobial Wound Dressing help injuries heal faster? Researchers checked Records of 38 patients who had been treated for acute or chronic wounds between 2010 and 2012. They found that those who had been treated with Procellera Healed almost twice as fast. This is a

Which of these is not an advantage of using a stratified sample instead of a simple random sample?