Question
MATH225 Statistical Reasoning for the Health Sciences
Week 1 Assignment Evidence, Claims and Study Types
Question A study was performed with a random sample of 5
people from a certain city. What population would be appropriate
for generalizing conclusions from the study, assuming the data
collection methods used did not introduce biases?
The conclusions should be restricted to only the city that
was sampled.
The conclusions are generalizable to all people on Earth.
The conclusions are generalizable to all people in the
country.
The conclusions apply only to the sample.
The conclusions apply to people in any city.
Question In the description of the following experiment,
determine the experimental factor. During a study testing a new
vaccine for Zika virus, the research team grouped the volunteers
enrolled for the test into Group A and Group B. Group A received an
inert drug (placebo) while Group B received the vaccine.
whether or not a person contracts the Zika virus
the effectiveness of the new vaccine
the drug received by each group
the group receiving the new vaccine
Question In a psychological study aimed at testing a medicine
for reducing stress levels, the researcher grouped the participants
into 2 groups and gave the stress-reduction pill to one group and a
placebo pill to another group. In the description of the above
situation, determine the experimental group.
The group that received the stress-reduction pill is the
experimental group.
The group that received the placebo pill is the experimental
group.
Both the groups are experimental groups.
Neither group is an experimental group.
Question A researcher is planning to conduct a study of the
effectiveness of an herbal tea for short term memory. The
experiment will involve people playing a short memory game multiple
times after taking either an ordinary tea or the herbal tea. Assume
both the teas look alike. Is informing the participants if their
tea is ordinary or herbal a good experimental design? Use your best
judgement.
No
Yes
Design of Experiments
Components of Experimental Design
In a designed experiment, the researchers deliberately
control some factors of the units that are being studied.
Typically, the objective of the research is to determine the effect
of the variation of one or more of the factors being controlled on
the response variables that are being measured.
Often, there is a single factor that is controlled, which has
multiple possible values. In many studies, the factor has the form
of a treatment applied to the individual units, so sometimes the
experimental factor is also called a treatment. Some examples of
kinds experimental factors are
•
the medication used to treat a medical condition
•
the fertilizer used for growing a crop
•
the method used to construct a widget
Typically, the research is interested in comparing the
effectiveness of new values for the experimental factor with an
existing standard value. A control group is included in the study
to provide a reference point for having no treatment or for using
the common or reference value of the experimental factor. In the
situations given above, the experimental factor for the control
group would be
•
a placebo, or inert treatment, or an existing treatment that is
already used
•
no fertilizer or the currently used fertilizer
•
the current process used to construct the widget
When the experimental units are people, applying treatments
that should be inert can actually have effects. This is known as
the placebo effect. So the control groups for studies that involve
people getting treatments should always be treated the same way as
the other groups. If the experimental treatment involves taking a
pill, the control group should also be given a pill that is inert.
This also raises a second issue with people involved in
studies. The key is that no person who can affect the outcome of a
study show know which experimental units have been given which
treatments. This is called blinding. In a single blind study, the
people receiving the treatments do not know what treatment they are
getting. This is to counteract the placebo effect.
In a double blind study, neither the people receiving the
treatments nor the researchers know which units receive which
treatments until after the experiment is complete and the data has
been collected. A double blind study is needed when the researchers
can affect the outcomes either intentionally or unintentionally.
Double blinding is commonly used in psychological studies and
medical studies.
Identify the Treatment
Question
A biology student is performing an experiment to examine the
effect of soil moisture on germination time for soy beans. He
plants 200 randomly selected soy bean seeds in containers that are
prepared as consistently as possible. The containers are all placed
under a controlled grow light. The plantings are then randomly
divided into four groups. One group receives no water, one group
receives 10 mL of water per day, one group receives 20 mL of water
per day, and the last group receives 30 mL of water per day.
Identify the experimental factor.
Question
In the description of the following experiment, determine the
experimental factor. A research team is testing a paste form of a
drug to alleviate inflammation. Participants are grouped into Team
A and Team B. Team A receives the paste form of the drug. Team B
receives a similar paste with no active ingredients.
Team A and Team B
the kind of paste received
the paste with the active ingredient
whether or not the paste helps the inflammation
Question To test the effectiveness of a drug proposed to
relieve symptoms of depression, psychiatrists recruited volunteers
for clinical tests. All of the volunteers were diagnosed with
symptoms of depression. The psychiatrists provided the drug to the
first group and a sugar pill to the second group. In the
description of the above situation, determine the experimental
group.
The group that received the drug is the experimental group.
The group that received the sugar pill is the experimental
group.
Neither group is an experimental group.
Both the groups are experimental groups.
Question In the description of the following
experiment, determine the experimental factor. A research team is
testing a product that will minimize wrinkles among older adults.
Volunteers in the age group of 40 to 45 are included in the
research. The research team gives a cream to be applied on the face
to one group and a placebo cream to the other group.
the average number of wrinkles in each group
the group receiving the active cream
the type of cream given to each group
the average reduction in wrinkles for each group
Question In a study to add a new feature to a software
program, the programmer introduced two categories, men and women,
in the survey she conducted. Is the study observational or
experimental? If it is an experiment, what is the controlled
factor?
The study is an experiment. The controlled factor is the
feature to be added in the software.
The study is an experiment. The controlled factor is the
category, men or women.
The study is an observational study.
The study is an experiment. The controlled factor is the
survey.
Question An energy drink manufacturer wants to find out the
effect of different amounts of their product on the maximum
anaerobic power level for rowers. Would an experimental or
observational study design be more appropriate?
An experimental study should be used with the maximum
anaerobic power as the controlled factor.
An experimental study should be used with the amount of the
drink consumed as the controlled factor.
An observational study should be used because the amount of
the drink consumed cannot be controlled.
An observational study should be used because the maximum
anaerobic power cannot be directly controlled.
Question A biology student is interested in the relationship
between temperature and germination time for soy beans. The student
gets sample seeds from multiple sources and randomly selects 180
seeds from them. Then he sets up three growing stations, one at
20?C, one at 15?C, and one at 25?C. He divides the seeds into three
groups of 60 and plants the seeds from each group in a growing
station. He records the germination time for each seed.
Is this an observational study or an experiment? If it is an
experiment, what is the controlled factor?
The study is an observational study.
The study is an experiment. The controlled factor is the
germination time.
The study is an experiment. The controlled factor is the
temperature.
The study is an experiment. The controlled factor is the
seeds.
Observational and Experimental Studies
There are two primary ways to collect data from a new sample:
an observational study and an experimental study. Both of these
methods involve choosing a sample of individuals from the
population and recording the value of one or more variables for
each individual. However, there are some differences.
In an observational study, no attempt is made to control any
aspect of the individuals in the sample. The sample is chosen using
an appropriate process, and the variables of interest are recorded
for each individual. This kind of study is typically used when it
is difficult, unethical, or impossible to control factors in the
sample. An observational study is also commonly used when there are
no factors that would need to be controlled. Here are a few
examples where an observational study would be used:
•
A study on the relationship between smoking and the risk of lung
cancer
•
A study on the relationship between premature birth and early
reading skills
•
A survey of the opinions of residents on a proposed addition to the
local school
In an experimental study, the researchers attempt to control
one or more aspects of the individuals in the sample. The
individuals in the sample will be randomly divided into multiple
groups or cases. Then the controlled factors will be set for each
of the groups as chosen by the researchers. This may be more clear
with a few examples of experimental studies:
•
Researchers randomly assign individuals to three groups. One group
listens to no music, one group listens to a top 40 channel from a
streaming service, and one group listens to individually selected
music. The researchers then give the subjects a cognitive test.
•
An agricultural agency divides 100 plots into two groups. One group
receives no pesticides and the other group receives pesticide
treatments. The crop yields of each plot are measured at the end of
the season.
Observational or Experimental?
Question A large manufacturing firm is interested in the
effect of the temperature of the manufacturing floor on worker
productivity. Over the course of a year, the firm randomly samples
its 103 sites and records the temperature and the quantity of items
produced on that day. Is this an experiment or an observational
study?
Question A study was conducted among school students on the
relationship between getting up late and getting to school late. Is
this an example of an observational study or experimental study? If
it is an experiment, what is the controlled factor?
The study is an observational study.
The study is an experiment. The controlled factor is getting
up late.
The study is an experiment. The controlled factor is getting
to school late.
The study is an experiment. The controlled factor is the
school students.
Question A consumer research company is interested in
determining if a certain company’s new refrigerator model is more
efficient than the older model. Researchers decide to investigate
the claim that the new model uses 10% less electricity than the
older model for the same cooling load. Which data collection method
is appropriate? Select only one answer choice.
The company should obtain random samples of people who own
each model and measure the electricity used over one month for each
refrigerator.
The company should obtain random samples of each model, place
them in similar conditions, fill them with the same amount of water
bottles, and monitor their electrical usage over one month.
The company should get a random sample of the new model,
place them all in similar conditions, fill them with the same
number of water bottles, and monitor their electrical usage over
one month.
The company should obtain one new model and one old model,
place them both in the same room, fill them with the same number of
water bottles, and monitor their electrical usage over one month.
Question A statistics student has obtained a sample by
surveying all the students in his class. What group can the results
of the survey be generalized to?
The conclusions should apply to all students at the college.
The conclusions should apply to students at any college.
The conclusions should apply only to the sample.
The conclusions should apply to all people.
Question A consumer research company is interested in
determining if a certain company’s new refrigerator model is more
efficient than the older model. What should the researchers do
first?
Write a claim about the efficiency of the new model that can
be tested.
Choose a random sample of the new models to perform testing.
Make some initial conclusions about the efficiency of the new
model.
Make some initial conclusions about the efficiency of the old
model.
Question A biologist wants to study the effect of vitamin D
enriched food on the weight of adult mice. Would an experimental or
observational study design be more appropriate?
An observational study should be used because the type of
food consumed cannot be controlled.
An observational study should be used because the weight of
adult mice cannot be controlled.
An experimental study should be used where the food consumed
is the controlled factor.
An experimental study should be used where the weight of
adult mice is the controlled factor.
Question In a survey conducted to find out the feedback of a
sports program organized in a club, the organizers asked the
respondents to classify their feedback as good, fair, poor, and
bad. Is the study observational or experimental? If it is an
experiment, what is the controlled factor?
The study is an observational study.
The study is an experiment. The controlled factor is the
feedback.
The study is an experiment. The controlled factor is the
ratings.
The study is an experiment. The controlled factor is the
respondents.
Question A pharmaceutical company conducted an experiment to
test a drug for controlling diabetes. The company enrolled
participants for the experiment and divided them into 2 groups. One
group received an inert drug and the other group received the
diabetes control drug. In the description of the above experiment,
determine the experimental group.
The group that received the inert drug is the experimental
group
The group that received the diabetic control drug is the
experimental group
Both the groups are experimental groups
Neither group is an experimental group
Question In the description of the following experiment,
determine the experimental factor. A team of physicians testing a
new liquid drug taken using an inhaler for treating colds gave the
drug to one group of volunteers enrolled for the test. They gave
the other group water using the same kind of inhaler.
whether or not the subject’s cold was cured
the type of liquid received by each group
the new liquid drug
all of the people in the study
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